An extension file usually adds extra abilities to your Macintosh. For example, a Chooser extension translates the data in your documents into a form that’s understood by a particular printer.

An extension is enabled by moving it in the Extensions folder. If the extension needs to be loaded into memory you must also choose Special ➡ Restart in the Finder. Numerous types of extensions are used, including system extensions, Chooser extensions, libraries, documents.

Installing and Using Extensions

Most extensions are provided by the Mac OS Installer or by an installer used for another application. By default, the Mac OS Installer automatically provide the standard Apple extensions, although you can also select Customize to add specific extensions.

You can also install an extension by dragging the file onto the System Folder, which automatically puts it in the Extensions folder. However, if you drag it into the System Folder window you must drag it manually into Extensions afterwards.

An extension or control panel containing INIT resources usually modifies the system at startup, often increasing the system’s memory requirements. To prevent INIT files from loading just press Shift during startup. This action also stops items in the Startup Items folder from launching.

Managing Extensions

An extensions management utility such as the Extensions Manager control panel lets you enable or disable extensions and control panels in sets. It operates by moving the specified extensions between the Extensions and the Extensions (Disabled) folders in the System Folder.

Extensions Manager shows a list of all available extensions as follows:-

As you can see, you can enable or disable an extension by simply clicking on its check box. Any changes you make are automatically saved in the current set, usually My Settings. However, you can always use Duplicate Set to create a new set which you can then modify independently.

Information about a highlighted item is shown in the optional pane at the bottom of the window. And by using the Preferences menu you can add columns that show the Type and Creator codes.


A conflict can occur if an extension containing an INIT resource changes part of the system that’s already been modified by a similar resource in another extension or control panel. This can cause a startup conflict or may upset the usual running of your computer.

During a normal startup, all the software necessary for the Mac system is extracted from the appropriate files in the System Folder and is loaded into memory. This operation is done in sequence, working through the files in the folders of the System Folder as follows:-

  1. Extensions
  2. Control Panels
  3. System Folder

Within this arrangement, each group of files is loaded in alphabetical order. In some instances a conflict can be avoided if the files are loaded in a different sequence. This means that it’s sometimes possible to eliminate a conflict by renaming an extension or control panel, as shown here:-

To load:Prefix name with:
EarlierBlank spaces
LaterTildes (~) or bullets (•)

You can also use extra letters or numbers in front of a filename in to ‘fine tune’ the loading sequence. Alternatively, you can move an offending file to a different folder. For example, a suitably named control panel in the Extensions folder will load before other other extensions or control panels.

Extension Types

Extensions use various mechanisms that have developed over a period of time. The Finder identifies these special files as particular Kinds, such as Apple Guide document, application program, Chooser extension, communications tool, document, library or system extension.

However, a much more accurate identification is provided by each file’s four-letter type code, as included in the following sections. The most common types of extensions are:-

Apple Guide Document poco mixn help

These documents provide extra information in the Help menu, but only when the Apple Guide extension is enabled. Although beginners may find the Apple Guide system helpful, the author finds it intensely irritating and condescending. If you’re inclined you can remove the Apple Guide extension and the Apple Guide files to save memory and disk space, although doing this can also upset the Help menu when used with the more modern Apple Help Viewer.

The following types of Apple Guide file are used:-

Application Program APPL

Applications that reside in the Extensions folder are automatically operated by other software, in most cases by the system itself. As always, memory is only used when the application is actually running, during which time the application can be reached from the application menu.

Chooser Extension PRER PRES RDEV

A Chooser extension lets you select a printer, scanner, special service or network facility from within the Chooser. The most common type is sometimes known as a printer driver. Chooser extensions aren’t loaded at startup and don’t use any memory until you actually start using them.

AppleShare is a slightly different kind of Chooser extension that lets you share items over a network. This extension always uses memory, even when you’re not actually using a network.

You can remove any items that you don’t want to see in the Chooser by simply disabling or removing the appropriate files in the Extensions folder. Drivers for some types of printer are not included in all versions of the Mac OS. Unfortunately, Apple doesn’t always indicate what should be used instead.

Communication Tool cbnd fbnd tbnd

A communications tool, also known as a basic connectivity tool, works with part of the system known as the Communications Toolbox (CTB). Each tool provides resources that supply extra menus and dialogue windows in any communications application that’s CTB-compatible.

Fortunately, each tool doesn't use any memory until needed. If a required tool is missing the application may fail or may simply tell you that the tool is missing. Several tools are provided with the Mac OS, although you may be end up with extra tools should you purchase extra hardware.


These are fairly uncommon in the System Folder, although you’ll find them in some sub-folders within the Extensions folder. You’ll also find items scattered around these folders that are associated with specific software, including files identified as a Sherlock document or a MPW document.

Library libr

This type of library often accommodates a feature in the Open Transport version of AppleTalk.

Library shlb

This type of library file provides programming code that’s available to any software. Most libraries contain native code for PowerPC-based machines, although a few support 680x0-based models.

System Extension appe thng ​ comd ndrv INIT scri

There are several varieties of system extension, including:-


The Extensions folder also contains folders, each containing software elements used by various parts of the system or by other applications. These folders often contain library files.

Standard Extensions

Below you’ll find details of extensions provided by Mac OS 8.6 through to Mac OS 9.1 and by other applications. Different versions of the system, unusual hardware or different software may result in less extensions or additional files. As the system has evolved some extensions have been combined into other files, often the System or Finder. Apple have also introduced new files to keep pace with developments in software and hardware. As a result there are now many more files but also a large number of outdated files. The extensions are listed as they appear in a List by Name view.

For further information about extensions you should refer to The InformINIT (D E Frakes). This is the only document that even approaches this daunting and rather frightening part of the Macintosh.

EM Extension INIT

For the Extensions Manager control panel, allowing you to press Space during startup for immediate access to the panel.

About Apple Guide poco

Provides information about the Apple Guide system in the Finder’s Help menu.

Altivec Enabler

Provides improved speed of operation with a G4 machine and any applications that support the Altivec technology used in this type of computer. Not suitable for older versions of the Mac OS.

Apple Audio Extension INIT

Accommodates various types of audio hardware on PCI PowerPC-based machines, including the conveyance of audio via USB ports. Appears to have been introduced with Mac OS 9.x.

Apple CD/DVD Driver INIT

A driver for an Apple CD-ROM or DVD drive. Third-party drives may require an alternative extension, in which case you’ll need to disable this file. The AppleCD Audio Player application requires this extension but may not work with third-party CD-ROM or DVD drivers.

Apple Colour SW Pro CMM thng

A Colour Matching Method (CMM) for ColorSync, ensuring consistent colours on an Colour StyleWriter Pro printer.

Apple Enet ndrv

Lets you use the built-in Ethernet card in your Mac.

Apple Guide INIT

Provides the Apple Guide system in the Help menu. Apple Guide files must also be present.

Apple Modem Tool cbnd

A communications tool, similar to Serial Tool, but with the added ability to control any modem that employs Hayes protocol. It allows the Mac-to-modem circuit to run at up 115.2 kbit/s or 230.4 kbit/s with suitable system software and hardware.

With a suitable application, you can select the type of modem, the appropriate serial port and type of error correction to be used. Then you can pick a phone number to dial and set the redial options. You can also choose the number of rings to allow before the modem answers an incoming call.

Apple Monitor Plugins INIT

Provides extra controls for AppleVision, ColorSync and other Apple monitors in the Monitors control panel. This appears to replace the °AppleVision extension used prior to Mac OS 9.x.

Apple Photo Access thng

Lets you browse through Photo-CD images on CD-ROM from within the Finder. To use it you must also enable the QuickTime and Foreign File Access extensions.

Apple QD3D HW Driver ndrv

Apple QD3D HW Plug-In shlb

Provides accelerated QuickDraw 3D, but only when the Apple QuickDraw 3D Accelerator Card or other suitable graphics hardware is available and when the QuickDraw 3D extension is enabled. The plug-in file contains a PowerPC-native library for accelerated operation. You may have turn off Virtual Memory in the Memory panel when using this feature on some machines.

AppleScript INIT

Lets you control scriptable applications using scripts created with Apple’s Script Editor or a similar application. This extension also includes a modern version of the Apple Event Manager.

AppleScriptLib shlb

A special library known as a glue library that allows PowerPC-native applications to use AppleScript. It works in Mac OS 7.x on a 680x0 machine, providing CFM-68K Runtime Enabler is present, although this isn’t required for a 68040-based machine running Mac OS 8.x.

AppleShare RDEV

A special Chooser extension that lets you share folders, files and printers over a network. This software shouldn’t be confused with Apple’s full server package, also known as AppleShare.

Application Switcher appe

A faceless background application that provides this panel for switching applications.

ATI 3D Accelerator shlb

ATI Driver Update ndrv

ATI Graphics Accelerator INIT

ATI MPP Manager shlb

ATI Radeon 3D Accelerator shlb

ATI Rage 128 3D Accelerator shlb

ATI Resource Manager shlb

ATI Video Accelerator thng

ATI Video Memory Manager shlb

These files are necessary for any PCI-based PowerPC model that has ATI video acceleration, either built-in or in the form of a graphics card. Support for three-dimensional (3D) hardware acceleration is also included. If you have problems with ATI graphics with Mac OS 8.6 you should obtain newer versions of these files, such as those supplied with the OpenGL package.

Audio CD Access thng

Lets you play an audio CD on your CD-ROM drive, assuming the Apple CD/DVD Driver and Foreign File Access extensions are also enabled. The drive mechanism can then be controlled using the AppleCD Audio Player or a compatible application.

Authoring Support INIT

Accommodates different types of CD-R or CD-RW drives in conjunction with Burn or iTunes.

Authoring Support Files Folder

Contains files for specific CD-R or CD-RW drives used with the Authoring Support extension.

CarbonLib INIT

This lets you use Carbonized applications that work in Mac OS X, as well as in Mac OS 8.1 or higher. Some applications require this file to be updated to a newer version while others may slow down with some versions of CarbonLib. At one stage it was reported that Entourage, supplied as part of Microsoft’s Office, was slowed down by CarbonLib version 1.4.

Claris Kermit Tool fbnd

A communications tool that lets you transfer files over a link using Kermit protocol, a mechanism that provides error protection. This is usually supplied with the ClarisWorks package.

Color Picker INIT

Provides improved methods for colour selection from within any application. If it’s not enabled the system provides a simple colour wheel, which is difficult to use for colour selection.

Color SW 1500 PRER

Lets you select an Apple Colour StyleWriter 1500 printer in the Chooser. The latest version of this file can also be used for the StyleWriter, StyleWriter II or StyleWriter 1200.

Color SW 2500 PRER

Lets you use an Apple Colour StyleWriter 2500, 2400 or 2200 printer.

Color SW Pro PRER

Lets you select an Apple Colour StyleWriter Pro printer in the Chooser.

ColorSync Extension INIT

This mechanism matches printed colours to those scanned into your machine or displayed on your monitor screen. A profile for your particular monitor must reside in the ColorSync Profiles folder inside the System Folder. The ColorSync control panel is also required.

This file is essential if you’re using the now-defunct QuickDraw GX extension in conjunction with Mac OS 7.x. However, you can save memory by disabling the ColorSync Extension file.

Contextual Menu Extension INIT

Provides contextual menus when you Control-click. For this feature you must have a Power-PC based machine with the SOMobjects for Mac OS extension enabled. Extra menu items can be added by putting additional files, each known as a Contextual Menu Module (CMM), into the Contextual Menu Items folder, inside the System Folder. In Mac OS 8.5 or higher you can install and remove CMMs within the control strip itself, and you don’t need to restart the machine.

Control Strip Extension appe

A background application that provides a control strip. The number of items that appear in the strip is determined by the files in the Control Strip Modules folder, inside the System Folder.

CSW 6000 Series PRER

Lets you use a Colour StyleWriter 6000 Series printer.

Default Calibrator shlb

For customising your monitor’s colour calibration from within the Monitors control panel in conjunction with ColorSync. The ColorSync Extension and associated files must also be enabled.

Desktop Printer Spooler appe

A background application that provides background printing for a desktop printer. Printing progress is monitored and controlled by the faceless Desktop PrintMonitor application.

Desktop PrintMonitor APPL

A faceless application program that supervises printing with a desktop printer in conjunction with the Desktop Printer Spooler extension. It requires the CFM-68K Runtime Enabler extension if you have a 680x0-based machine running Mac OS 7.x.

Disc Burner Extension scri

Lets you burn CD-R and CD-RW discs using Apple’s Disc Burner application. Also requires the Authoring Support extension and an appropriate file in the Authoring Support Files folder.

DNSPlugin shlb

A shared library that used by recent Internet applications.

DrawSprocketLib ​ shlb

A shared library used for graphics in some types of computer games. If preferred, to reduce the clutter in your Extensions folder you can move this file, along with all of the other ‘sprocket’ files, to the Application Support folder, inside the System Folder.

DVD Decoder Library shlb

DVD PC Card Enabler ndrv

DVD Region Manager INIT

Required for reading information from DVD discs.

FBC Indexing Scheduler appe

A background application that lets the Sherlock application index your volumes at prescribed times.

File Sharing Extension INIT

Allows you to share files and folders over a network.

File Sharing Library shlb

Used by the File Sharing control panel.

Find Folder

A folder containing resources that are used by Sherlock when searching in text.

Find by Content shlb

Enables Sherlock to perform a Find by Content search after indexing your drives.

FireWire CardBus Enabler ndrv

FireWire Enabler ndrv

FireWire Support expt

Required for transferring any kind of data via a FireWire interface.

Folder Actions appe

A faceless application used in Mac OS 9.x to run AppleScript scripts attached to folders.

FontSync Extension appe

A faceless application used in Mac OS 9.x to provide font matching in applications and scripts.

Foreign File Access INIT

For reading non-Mac CD-ROM disk formats such as High Sierra or ISO 9660. The appropriate extensions for these two formats must also be enabled.

Global Guide Files Folder

A folder that contains Apple Guide files for general information that applies to any type of computer.

Heidelberg CMM thng

A Colour Management Module (CMM) supplied with ColorSync.

HTMLRenderingLib ​ shlb

Allow applications such as Help Viewer to display HTML content in Mac OS 9.x.

High Sierra File Access thng

For reading a non-Mac CD-ROM that’s formatted to the High-Sierra (HS) standard. The Foreign File Access extension must also be enabled.

ImageWriter PRES

Lets you use an Apple ImageWriter or ImageWriter II printer.

Indeo® Video thng

A special file sometimes added when you install Microsoft Internet Explorer or a similar application. It contains a codec that works with QuickTime to encode or decode any video file using the R3.2 format, or to decode any file that’s encoded to the R3.1 standard.

Intel Raw Video thng

Sometimes provided when you install Internet Explorer or a similar application. It contains a codec that works with QuickTime to encode or decode any video file using the raw video (YVU 9) format.

InputSprocket Extension shlb

Provides Mac OS 9.x support for various controllers used in computer games. This appears to replace the older files listed below, although it doesn’t seem to support the same amount of hardware.

InputSprocket ArenaMouse shlb

InputSprocket CH shlb

InputSprocket CH Trackball shlb

InputSprocket Contour shlb

InputSprocket Gravis shlb

InputSprocket Kensington shlb

InputSprocket Keyboard shlb

InputSprocket MacALLY shlb

InputSprocket Microspeed shlb

InputSprocket Mouse shlb

InputSprocket NoHandsMouse shlb

InputSprocket SideWinder 3D Pro shlb

InputSprocket Speech shlb

InputSprocket Thrustmaster shlb

InputSprocket AppleJack shlb

InputSprocket USB shlb

InputSprocketLib ​ shlb

Libraries for various controllers used for computer games, apparently replaced by the InputSprocket Extension in Mac OS 9.x. To reduce the clutter in your Extensions folder you can move these files, along with other ‘sprocket’ files, to the Application Support folder, inside the System Folder.

Internet Access shlb

Required by Apple software such as Internet Setup Assistant. It uses the Internet Configuration System (ICS), provided on the Mac by the Internet Config Extension. Not used in Mac OS 9.x.

Internet Config Extension ​ thng

This lets you keep track of settings for all Internet applications by using the Internet Configuration System (ICS). Settings are entered once, using the Internet control panel, Internet Config application or any application compatible with ICS. Some software installers replace later versions of this extension, designed for use with the Internet control panel, by an earlier incompatible version.

Internet Config RandomSignature ​ thng

Demonstrates the operation of the Internet Config Extension, but not supplied with Mac OS 9.x.

Iomega Driver INIT

A special extension that automatically mounts any kind of Jaz, Zip or Floptical cartridge.

IrDA Tool cbnd

A communications tool that gives access to a computer’s infrared port using IrDA protocol.

IrDALib shlb

Conveys data to the infrared port by means of IrDA protocol, as used by non-Apple devices. This file or the Infrared panel shouldn’t be used on older models that don’t support IrDA.

IrLanScannerPPC ​ libr

For registering a network over an infrared port. This file or the Infrared control panel shouldn’t be used on older machines that don’t support the IrDA standard. Not used in Mac OS 9.x.

ISO 9660 File Access thng

Lets your machine read non-Mac CD-ROM discs that conform to the ISO 9660 standard. The Foreign File Access extension must also be enabled.

iTunes Extension INIT

Lets you use the iTunes application for playing MP3 audio files and CD audio discs.

LaserWriter 300/LS PRER

For a Personal LaserWriter 300, Personal LaserWriter LS or LaserWriter Select 300 printer.

LaserWriter 8 PRER

This Chooser extension accommodates printing with any a PostScript laser printer that has a suitable PostScript Printer Definition (PPD) file located in the Printer Descriptions folder.

To use a printer with an AppleTalk connection you must also enable the Shared Library Manager and all of the files associated with the Open Transport form of AppleTalk.

The extension can also print to an Encapsulated PostScript file (EPSF) without requiring an actual printer or the Open Transport software. Just select LaserWriter 8 in the Chooser, activate AppleTalk in the dialogue and proceed with printing.

PrintingLib must be enabled in order to use LaserWriter 8 in any mode. In older systems the Finder Help extension is also required and if you’re using Mac OS 7.x on a 680x0-based machine you must also enable the CFM-68K Runtime Enabler extension.

LDAP Client Library shlb

LDAPPlugin shlb

Lets your computer get information from directory services on an LDAP Directory Server.

Location Manager Extension AINI

Enables the Location Manager control panel.

Location Manager Guide poco

Provides additional information under the Help menu concerning the Location Manager panel.

Location Manager Modules Folder

Contains files that define what elements can be set by the Location Manager control panel.

MacinTalk 3 thng

MacinTalk Pro thng

Provides speech synthesis, using the appropriate voice files located in the Voices folder. The Speech Manager extension and the Speech control panel must also be enabled.

The MacinTalk 3 speech synthesiser was originally designed for faster 68030-based machines. However, the MacinTalk Pro system provides superior speech on the fastest 680x0 models or on a PowerPC-based machine. Both versions of MacinTalk can be active at the same time.

Macintosh Guide help

Provides the basic Apple Guide information that appears under the Finder’s Help menu.

MacLinkPlus for Easy Open thng

Provides automatic file translation in conjunction with the File Exchange control panel. The Shared Library Manager extension should also be enabled to accommodate any translator files. This extension is not a standard component but is supplied as part of MacLinkPlus from DataViz.

Microsoft Component Library shlb

Used by some Microsoft applications for handling data that includes Object Linking and Embedding (OLE). Apparently this file can upset the Office 98 package.

Macromedia Folder

Contains files used by Shockwave and other Macromedia products.

Modem Scripts Folder

Contains modem scripts, also known as Connection Control Language (CCL) scripts, each of which supports a specific type of modem. They appear in the Remote Access or Modem control panels for Internet access and also in any application that uses Apple’s standard Communications Toolbox (CTB). They also appear in the PPP panel used in older versions of the Mac OS. Some older applications may prefer to store these documents as loose items in the Extensions folder.

MRJ Libraries Folder

Contains the MRJLib file and other items required for Mac OS Runtime for Java™. This is required if you want to see all the really clever stuff that’s provided on some Web pages.

MS Font Embed Library (PPC) shlb

Used by some Microsoft applications to embed the actual fonts into a document. This file is provided alongside older versions of Internet Explorer and Office 98 but not with Mac OS 9.x.

MS Library Folder Folder

Contains shared libraries used by older versions of Internet Explorer and by Office 98.

Multi-User Startup scri

Provides logging-on feature for users at startup in Mac OS 9.x.

Multiprocessing ​ Folder

Contains special libraries required by applications that support a machine containing multiple processors. However, machines with a single processor are still required to have this folder.

NBP Plugin shlb

Lets your computer receive listings of network objects from NBP.

NetSprocketLib shlb

A shared library used for Internet operation of some types of computer games. To reduce the clutter in your Extensions folder you can move this file, along with all of the other ‘sprocket’ files, to the Application Support folder, inside the System Folder.

Network Setup Extension shlb

A library used by the AppleTalk, Modem, Infrared, Remote Access and TCP/IP panels.

Nomad II USB Driver ndrv

Nomad MG USB Driver ndrv

Nomad USB Shim ndrv

NomadJukeboxLib ​ shlb

For using a Nomad MP3 player with iTunes.

NSL UI Library shlb

Lets applications in Mac OS 9.x use a standard ‘Get URL’ dialogue to find Internet services.

Open Transport otsl

Open Transport ASLM Modules libr

Files that support Open Transport in Mac OS 9.x, replacing some of the older files shown below.

OpenGLEngine shlb

OpenGLLibrary shlb

OpenGLMemory shlb

OpenGLRenderer ​ shlb

OpenGLRenderer​ATI ​ shlb

OpenGLUtility shlb

Provides support for the OpenGL graphics system, as widely used for computer games.

Open Tpt AppleTalk Library libr

Open Tpt Internet Library libr

Open Transport Library libr

OpenTpt Modem libr

OpenTpt Remote Access libr

OpenTpt Serial Arbitrator libr

A set of Shared Library Manager documents used for Open Transport in Mac OS 8.x. The OpenTpt Serial Arbitrator file allows a common serial port to be shared between by normal Internet applications and other software used to gain access to a remote network or computer. The first four of these files are replaced by Open Transport and Open Transport ASLM Modules in Mac OS 9.x.

OpenTptAppleTalk​Lib shlb

OpenTptInternetLib ​ shlb

OpenTransportLib ​ shlb

Shared library files that provide non-native Open Transport system software in Mac OS 8.x. These files are replaced by Open Transport and Open Transport ASLM Modules in Mac OS 9.x.

PowerBook G3 Series Modem ndrv

Lets you use the internal modem in a PowerBook G3 computer.

PPP Connect Scripts Folder

Contains scripts used by the Modem or PPP control panel.

Printer Descriptions Folder

Contains Postscript Printer Definition (PPD) files used by the LaserWriter 8 Chooser extension. You can remove any PPDs intended for a model of printer that you don’t use.

Printer Share INIT

Lets you print via a network to a non-AppleTalk printer connected to a serial port of another machine. This extension must be enabled on both machines in order for it to work.

Printing Plug-ins Folder

This folder can contain extra files used for printing.

PrintingLib shlb

For use with the LaserWriter 8 Chooser extension, providing QuickDraw to PostScript conversion. This ‘fat’ library works with both PowerPC and 680x0-based models but requires the CFM-68K Runtime Enabler when using Mac OS 7.x.

PrintMonitor APPL

An application that can be used to supervise printing when the Desktop Printer Spooler extension is disabled. With background printing enabled the faceless Desktop PrintMonitor application performs this role.

QD3DCustom​Elements shlb

Allows QuickDraw 3D shapes to be assigned URLs and names. Requires QuickDraw™ 3D (see below) and other related extensions.

QuickDraw™ 3D INIT

Allows applications to view and create three-dimensional (3D) images. Other extensions may also be required, depending on the software and hardware that you use.

QuickDraw™ 3D IR shlb

Provides interactive rendering in a 3D application. Also requires the QuickDraw™ 3D extension.

QuickDraw™ 3D RAVE shlb

For using a 3D Accelerator Card or other suitable graphics hardware with a 3D application. Also requires QuickDraw™ 3D.

QuickDraw™ 3D Viewer shlb

Lets you to view 3D files by means of suitable applications, including recent versions of SimpleText and the Scrapbook. Also requires the QuickDraw 3D extension.

QuickTime Extensions Folder

Contains codec files that extend the abilities of QuickTime.

QuickTime™ INIT

Provides enhanced features for applications that handle movies, graphics, sounds and MIDI documents. Also provides automatic file compression of PICT files in any application and can be used to create a preview image for each file. Most users should leave this extension enabled.

QuickTime™ MPEG Extension INIT

Provides controlled viewing of MPEG-compressed multimedia files, including Layer-I and Layer-II audio streams, from within any QuickTime application. It requires a PowerPC-based machine and at least 2.5 MB of free memory per MPEG bit stream. To use this extension you must also enable the QuickTime™ extension. It may be incompatible with some third-party MPEG playback cards.

To view MPEGs from within your Web browser you must install the QuickTime Plug-In file.

QuickTime™ Musical Instruments INIT

Contains 30 standard MIDI sounds that can be played from a QuickTime application without requiring any external MIDI equipment. This extension requires QuickTime™ to be enabled.

QuickTime™ PowerPlug INIT

Provides native QuickTime operation on a PowerPC-based machine by means the QuickTimeLib library contained in the file. This extension requires QuickTime™ to be enabled.

QuickTime™ VR INIT

Allows a QuickTime application to view virtual reality (VR) images. This extension requires QuickTime™ and QuickTime™ PowerPlug extensions to be enabled.

Remote Only adev

Lets you run AppleTalk and an AppleTalk-related application at the same time as using both the Printer and Modem ports for non-AppleTalk serial devices. Often used with Remote Access.

Security Library shlb

Security Manager shlb

Security Policy Module shlb

Security Storage Module shlb

These files are used by Keychain Access, Apple Verifier and other applications that use the security features built into Mac OS 9.x.

Serial (Built-In) libr

For running AppleTalk via a serial port, usually by means of LocalTalk hardware. Some models of computer will fail at startup if this extension isn’t enabled.

Serial Tool cbnd

A communications tool that can transfer data via any serial port. This includes integral Modem or Printer ports or additional ports provided by a CTB-compatible expansion card. This tool optimises the link, even when another tool, such as Apple Modem Tool is used to accommodate a special device or protocol. So don’t remove this file if you intend to use any CTB-compatible applications.

SerialShimLib shlb

This file supports serial interfaces such as USB and IrDA in Mac OS 9.x.

Shared Library Manager INIT

Shared Library Manager PPC INIT

Allows the object-orientated code in a shared library file to be shared. This extension is required for AppleTalk as well as for file translation and other special software. The second extension is necessary for native support on a PowerPC-based machine.

ShareWay IP Personal Bgnd APPL

This application lets you to share your files using TCP/IP, as enabled using the File Sharing control panel in Mac OS 9.x.

SimpleText Guide Help

Provides appropriate Apple Guide information under the Help menu when SimpleText is in use.

SLPPlugin shlb

For receiving network information via the Internet.

Software Update Engine APPL

Software Update Scheduler appe

Lets you manually or automatically update your Mac OS 9.x software over the Internet.

SOMobjects™ for Mac OS shlb

This standard object model (SOM) was devised by IBM for the OS/2 operating system used on PCs. It was also employed on the Mac for Apple’s abandoned OpenDoc system. This extension should be enabled, since it’s used for various features, including contextual menus. Apparently it reduces application size by providing commonly-used code.

Sound Manager INIT

Supports the built-in sound facilities in your machine, providing sound mixing by means of QuickTime. This extension is necessary for games and some sound applications.

SoundSpace2Lib ​ shlb

Used by iTunes for external MP3 players.

SoundSprocket Filter thng

Used for 3D audio effects in games when the SoundSprocketLib extension is enabled.

SoundSprocketLib ​ shlb

Provides enhanced sound in some games. To reduce the clutter in your Extensions folder you can move such ‘sprocket’ files, to the Application Support folder, inside the System Folder.

SpeakableItems INIT

Allows the computer to recognise spoken commands. Speech Recognition must also be enabled.

Speech Manager INIT

Gives SimpleText and other applications the ability to read out documents and enables the Finder to speak dialogue messages. The Speech panel and a MacinTalk extension should also be enabled.

Speech Recognition INIT

Provides speech recognition (SR) on an AV Mac or any PowerPC-based machine. The Speech control panel must also be enabled.

StuffIt Engine™ shlb

StuffIt Plug-ins Folder

StuffIt Engine™ PowerPlug shlb

StuffItEngineShell ​ shlb

These components are supplied as part of Aladdin’s StuffIt Expander and other products, allowing your machine to compress files into various formats or to expand them back again. StuffIt Engine™ PowerPlug is only used by older StuffIt products, while StuffIt Plug-ins, containing files for different file types, and StuffItEngineShell are used in version 7 software or higher.

StyleWriter 1200 PRER

Lets you use an Apple StyleWriter, StyleWriter II or StyleWriter 1200 printer. This is replaced by the Color SW 1500 file in Mac OS 9.x.

SystemAV thng

A mechanism that provides hardware information for the Monitors or Monitors & Sound control panel. This extension is replaced by System Monitor Plugins in Mac OS 9.x.

System Monitor Plugins thng

A Mac OS 9.x file that provides hardware information for the Monitors control panel, replacing the older SystemAV extension.

Text Encoding Converter shlb

Deals with different encoding methods, including ISO-8869, Unicode and those used by other operating systems such as the Mac OS and Windows. Each system uses a file from the Text Encodings folder, inside the System Folder.

This is essential if your drives are formatted with HFS+ and is required by Microsoft Internet Explorer and other applications. On a 680x0-based machine running Mac OS 7.x you must also enable the CFM-68K Runtime Enabler extension.

Text Tool fbnd

A communications tool for transferring plain text files over a link without any form of error correction. Although rarely used this can be handy for transferring data directly between a Mac and another computer via one of the serial ports.

Time Synchroniser appe

A background application that allows you to synchronise the setting of your Date & Time control panel with a network time server or from the master time clock on a local network.

TTY Tool tbnd

A communications tool that emulates a Teletype (TTY) device. It can be used in place of ANSI or VT-120 protocols when making a connection to a bulletin board service (BBS) or for a direct connection to another modem from your own computer and modem.

Type 1 Scaler sclr

Allows ATSUI applications to use PostScript fonts.

UDF Volume Access INIT

For reading disks, usually DVD-ROM, that are prepared to the Universal Disk Format (UDF).

URL Access otsl

Allows your computer to retrieve information from remote Internet sites.

USBHIDUniversal​Module ndrv

Required for some USB games controllers, although not provided as a separate file in Mac OS 9.x. Also needs the ‘sprockets’ series of files.

USB Printer Sharing Extension appe

Allows a USB-connected printer to be used over a network.

USBNomad​JukeboxDriver ndrv

USBRioDriver ndrv

USBSoundSpace2​Driver ndrv

Used by iTunes for external MP3 players.

Video Out Default (PAL) ndrv

Switches the default video output of your computer from the American NTSC television standard to the European PAL standard.

Video Startup INIT

Lets you use the Apple Video Player application, but not required for the MacTV.

Voices Folder

Contains voice files for all versions of MacinTalk speech synthesis. The 2, 3 or P characters on each voice icon indicates which of the MacinTalk 2, MacinTalk 3 or MacinTalk Pro extensions it uses.

VT102 Tool tbnd

A communications tool that allows a Mac to emulate a simple VT-102 computer terminal.

Web Sharing Extension APPL

An application that works with the Web Sharing control panel to provide a personal Web server.

XMODEM Tool fbnd

A communications tool that lets you send files over a communications link by means of the XMODEM protocol, a system that uses a standardised form of error correction.

°AppleVision INIT

Required if you have an AppleVision video monitor and an older system. However, this extension has been replaced by Apple Monitor Plugins in Mac OS 9.x.

Additional Extensions

Most of the extensions already described come with modern versions of the Classic Mac OS. Those listed below are sometimes included with a particular application or software package, although there are many others. For example, Microsoft provides the Shared Code Manager extension which provides Object Linking and Embedding (OLE). This system is similar to Publish and Subscribe or Apple’s abandoned OpenDoc system and lets you embed one document into another, such as an Excel worksheet into a Word file.


For enhanced PostScript printing with any printer that has a PostScript Printer Definition (PPD) file inside the Printer Descriptions folder. It works in a similar way to the LaserWriter 8 extension, providing PostScript Level 3 printing, printer switching and two-pass background printing.

Apple Colour Printer PRER

For an Apple Colour Printer.

Apple Scan

For a scanner, usually an Apple model, but also suitable for some third-party devices.

AppleTalk ImageWriter PRER

For an Apple ImageWriter II printer operating via AppleTalk.

At Ease Startup INIT

Makes your computer starts up with At Ease, a system that replaces the Finder with a simplified environment and program launcher. For this to work you must have the actual At Ease file inside the System Folder, together with the At Ease Items folder.

Colour StyleWriter 6000 PRER

Lets you use an Apple Colour StyleWriter 6000 printer.

Colour SW 2000 Series CMM thng

A Colour Management Module (CMM) used by the ColorSync extension to ensure consistent colours on any printer in the Apple Colour StyleWriter 2000 series.

Contextual Menu Enabler INIT

Allows a contextual menus to be used in applications that don’t otherwise support them. This means you can use the Internet Address Detectors (IAD) plug-in, part of the Apple Data Detectors (ADD) package, allowing you to pick a URL from a selected area of text and then choose an action to be taken, such as calling up the URL with your Web browser application.

CSW 4000 Series PRER

Let you use an Apple Colour StyleWriter 4100 or 4500 printer.

CSW 4000 Series (AT) PRER

Let you use an Apple Colour StyleWriter 4100 or 4500 printer with an AppleTalk connection.

Cyberdog Extension INIT

For Cyberdog, a rather nifty OpenDoc-based Internet application from Apple whose development sadly came to an end.


A communications tool for applications that employ Data Access Language (DAL), a system for interrogating databases on Unix-based computers. This also works with the ANSI-standard Structured Query Language (SQL) as well as other database servers such as IBM’s DB2 and Informix, as used on VAX computer systems.

Desktop Printer Menu INIT

Gives access to all of your desktop printers via a special menu in the menu bar.


Lets you add a digital signature to any document, as originally supplied as part of PowerTalk.

Fax Sender

For sending a fax from within any application by means of a GeoPort modem.

FreeMIDI System Extension INIT

Lets you use any FreeMIDI-based music application with other MIDI software or hardware.


Creates high-quality image files for a Genigraphics service bureau, although PostScript is now the preferred file format. As supplied with Microsoft Office and other applications.


For sending a fax from within any application by means of a Global Village modem. When you press the Option key the Print item in the application’s File menu changes to Fax.


Lets you visit the site of a URL by means of -clicking on the URL in a document . However, this only works in applications that use Apple’s TextEdit editing mechanism. In addition, isn’t necessary for reaching URLs from within applications that already support Internet Config.

ImageWriter LQ PRER

Lets you use an Apple ImageWriter LQ printer.

JavaScript thng

An interesting extension from Late Night Software Ltd that lets you write scripts in the JavaScript language within Apple’s Script Editor application.

jgdw.68K shlb

jgdw.ppc shlb

Allows Microsoft Internet Explorer to decode graphics files that have been compressed using the Johnson-Grace method. The files are for a 680x0 or PowerPC machine respectively.

Joliet Volume Access INIT

Another third-party extension, this time from Miles Software, that lets you view the content of all types of CD-ROM, including the Mac and non-Mac areas of such discs.


Provides an alternative Colour Management Module (CMM) for use with ColorSync, working in place of the standard Apple CMM supplied with the system. Usually provided alongside a set of the KODAK PRECISION files.

KODAK PRECISION… series thng

These Kodak Precision Colour Management System (CMS) files, as well as the CMSCP and KPCMS folders in the System Folder, are supplied with some applications that operate with Kodak Photo-CDs. These files can usually be removed if you don’t actually use this type of CD.

LaserWriter IISC PRER

Lets you use an Apple LaserWriter IISC printer connected to the computer via its SCSI port.

LaserWriter Select 300 PRER

Lets you use an Apple LaserWriter Select 300 printer.

LaserWriter Select 310 PRER

Lets you use an Apple LaserWriter Select 310 printer.

LQ AppleTalk ImageWriter PRER

Lets you use an Apple ImageWriter LQ printer connected via AppleTalk.

LQ ImageWriter PRER

Lets you use an Apple ImageWriter LQ printer. Apparently, this replaces the ImageWriter LQ file.

Mouse Keys

Lets you use the keys in vicinity of the K key on an older type of PowerBook as a numeric keypad. The feature is activated by pressing -Shift-Esc and disabled by pressing Esc. More modern PowerBook models have a similar feature built into the machine’s hardware.

OMS Emulator

Lets FreeMIDI-based and OMS-based music applications share common serial ports for MIDI connections. Also allows OMS applications to run inside the FreeMIDI system.

Open Music System INIT

Lets you run an OMS-based application with other MIDI software or hardware.

PANTONE® Colour Picker

An alternative colour picker that displays calibrated Pantone colours from the Pantone Colour Matching System (CMS). Apparently, an AppleVision or ColorSync monitor must be used and the ColorSync and Color Picker extensions enabled.

PC Clipboard Translators

Lets you copy and paste data between the PC operating system used on a DOS Card fitted in a Mac and standard applications running under the Mac OS.

PDF Writer

Lets you create Portable Document Format (PDF) documents from within any application. Simply select PDF Writer in the Chooser and choose File ➡ Print. And you can avoid the Chooser by holding down the Control key whilst selecting Print. The resultant file can be read on any machine by using the freeware application known as Adobe Reader or Acrobat Reader (Adobe).

Personal LaserWriter SC PRER

Lets you use Personal LaserWriter SC or LaserWriter IISC printer connected via the SCSI port.

Portable StyleWriter PRER

Lets you use an Apple Portable StyleWriter printer.

StyleWriter II PRER

Lets you use an Apple StyleWriter II printer. A more recent version of the StyleWriter 1200 or Color SW 1500 extension should be used in place of this file.

Text Preview thng

Lets you preview the text in an ClarisWorks document from within an Open dialogue.

XTND Power Enabler shlb

A glue library that gives access to the non-native Claris XTND System, as used by ClarisWorks and other applications to provide file translation on a PowerPC-based machine.

ZMODEM Tool fbnd

A communications tool for sending files over a link using ZMODEM, a standard protocol with its own form of error correction.

Outdated Extensions

As the Mac evolved, many extensions were abandoned or built into other parts of the system. The following list gives details of files that aren’t needed in Mac OS 8.x or Mac OS 9.x. For the sake of simplicity, many items used before Mac OS 7.5, such as enablers or bug fixes, have been omitted.

CFM-68K Runtime Enabler INIT

Allows a 680x0-based computer to partially imitate the Code Fragment Manager (CFM), as used in a PowerPC-based machine. This allows an application that uses libraries to run faster with reduced memory requirements and is essential if you want use desktop printing, OpenDoc or a modern versions of LaserWriter 8. Its functions are built into the System file in Mac OS 8.x.

Display Enabler INIT

This extension is used for an Apple AppleVision, AudioVision or any other type of multi-scan or multi-sync monitor. It lets you change the screen resolution in the Monitors & Sound control panel at any time and adds features to Energy Saver panel that’s used in a PCI-based PowerPC.

3-Hole Punch uspt

A paper type for use with QuickDraw GX.

7200 Graphics Acceleration INIT

For a PowerMac 7200 fitted with a video card in a PCI slot.

7200 Graphics Driver INIT

Accommodates the motherboard video system fitted in a PowerMac 7200. The functions of this file are built into the System file in Mac OS 8.x.

9600 Graphics Accelerator ndrv

For the IMS video card fitted in a PowerMac 9600.


The Apple Real-Time Operating System (A/ROSE) for running a network. Only required when using an Apple Token Ring 4.16 NB, Apple Serial NB or any similar outdated NuBus card that’s based on the Macintosh Co-processor Platform (MCP).

Appearance Extension INIT

Gives the Finder in Mac OS 8.x its unique Platinum appearance, including three-dimensional (3D) icons, a border around each window for dragging and a roll-up button at the top right-hand corner of each window. You can also roll-up a window by double-clicking on its drag bar.

This extension also lets you choose an alternative system font for menus, provides tick-style check boxes and installs a new Help menu alongside application menus, replacing the older menu positioned at the end of the menu bar.

Apple 10/100 Fast Ethernet ndrv

For a PCI PowerPC that’s equipped with an auto-sensing Ethernet port. This type of port can run at the standard speed of 10 Mbit/s or at the Fast Ethernet speed of 100 Mbit/s.

Apple Built-In Ethernet comd

For a 680x0-based Mac fitted with a standard Ethernet port.


A driver for a standard Apple CD-ROM drive. Third-party drives often require an alternative extension, in which case you should disable this file.

Apple Ethernet CS comd

For an Ethernet card fitted into the Communications Slot (CS) in a 680x0-based Mac. This file can be disabled if you don’t have this kind of card.

Apple Ethernet CS II ndrv

For an Ethernet card fitted into the Communications Slot (CS) in a PowerPC-based Mac. This file can be disabled if you don’t have this kind of card.

Apple Ethernet LC comd

For an Ethernet card fitted into the LC Slot in a 680x0-based machine: can be disabled if you don’t have this kind of card.

Apple Ethernet NB comd

For an Ethernet card fitted into a NuBus slot in a 680x0-based machine: can be disabled if you don’t have this kind of card.

Apple Events Manager INIT

Supervises the Apple Event messages sent between applications. Its functions are built into the AppleScript extension that’s used in Mac OS 8.x and Mac OS 7.6.1.

Apple PCI Token Ring ndrv

For a Token Ring card fitted into a PCI slot in a suitable PowerPC-based machine. This file can be disabled if you don’t have this kind of card.

Apple Remote Access Client LTMC

Lets you use Apple Remote Access (ARA) on your mobile computer. This has been replaced by newer Open Transport software, including the modern Remote Access control panel.

Apple Token Ring NB comd

For a Token Ring card fitted into in a NuBus slot in a 680x0-based machine: can be disabled if you don’t have this kind of card.

Assistant Toolbox INIT

Enables the File Assistant application for a PowerBook, although it also works on other machines. This extension is built into the System file for Mac OS 8.x and Mac OS 7.6.1.

Caps Lock INIT

Shows an upward arrow in the menu bar when Caps Lock is selected on a PowerBook. This isn’t needed for the PowerBook 500 series and is inside the Finder file in some versions of the Mac OS.

Catalogues Extension fext

Provides desktop access to catalogues for PowerTalk.

Clipping Extension fext

Lets you use drag and drop selected data to create a clipping file on the desktop. However, drag and drop between applications still works even without this extension. The functions of this extension are built into the Finder file in Mac OS 8.x.

ColorSyncLib68K shlb

For using earlier versions of the ColorSync extension on a 680x0-based machine, in conjunction with the CFM-68K Runtime Enabler extension.

Desktop Printer Extension fext

Provides any number of desktop printers, each of which is initially selected in the Chooser. Requires the CFM-68K Runtime Enabler extension on a 680x0-based machine. The functions of this file are built into the Finder file in Mac OS 8.x.

ENET Compatibility comd

For Ethernet operation using a PCI-based PowerPC connected to a Novell Netware network.

EPSExtension pext

A printing extension that appears in the Printing menu when the QuickDraw GX extension is present. It lets you create an EPSF document from the LaserWriter GX Chooser extension.

Energy Saver Extension INIT

Lets you use the Energy Saver control panel that’s designed for a PCI-based PowerPC.

Ethernet (Built-In) ndrv

For a built-in Ethernet port, as fitted to some PCI-based PowerPC models.

EtherTalk Phase 2 adev

For the operation of a modern EtherTalk network.

EtherTalk Prep

For an EtherTalk network. This file’s functions are built into the System file in Mac OS 8.x.

Find File Extension INIT

Lets you launch the Find File application by pressing -F. If disabled you’ll be limited to the system’s simple Find facility. This extension is built into the Finder file in Mac OS 8.x.

Finder Extensions Enabler INIT

A non-Apple extension that lets you press -Delete to move a file to the Trash or press -R to select Reveal Original for an alias. You can also use Control-drag to create an alias from a file. Some of these features are also included in Mac OS 8.x.

Finder Help help

Provides Balloon Help in the menu bar and is also required by some versions of the LaserWriter 8 extension. Its functions are built into the Apple Guide extension in Mac OS 8.x.

Finder Scripting Extension fext

Allows AppleScript to send instructions to the Finder. Some utility applications won’t work without this extension. This file’s functions are built into the Finder file in Mac OS 8.x.

GXGraphics INIT

A cut-down version of the original QuickDraw GX extension (see below), which gave enhanced graphics in Mac OS 7.x but was incompatible with Mac OS 8.x. This extension also allows limited use of the ‘GX’ Chooser extensions when running Mac OS 7.x.

IIci/IIsi Monitors Extension INIT

Adds options to the Monitors control panel for the video card in a Mac IIci or IIsi computer.

IRTalk adev

Lets your computer use the IRTalk standard to convey data via its infrared port.

Inline Support INIT

For inline character entry, as required when using Speech Recognition and AppleScript to send commands to the computer.

InputBackSupport INIT

Required by the WorldScript extension to accommodate two-byte oriental fonts.

LaserWriter 8f PRER

Similar to LaserWriter 8 but accommodating fax options for the LaserWriter 16/600. Unfortunately, using this extension removes the LaserWriter 8 preferences file, so you’ll need to use Setup in the Chooser whenever you want to return to the normal LaserWriter 8. In Mac OS 8.x this extension has been replaced by an updated version of LaserWriter 8.

LC Monitors Extension INIT

Adds options to the Monitors control panel for a Mac LC with built-in video card. This software supports scan rates of 60, 67 and 75 Hz, including VGA at 60 Hz.

Letterhead uspt

A paper type for the QuickDraw GX system.

Link Tool Manager aini

Establishes a modem connection with Apple Remote Access (ARA).

LocalTalk PCI

A PowerPC-native driver for LocalTalk network hardware. If you have problems selecting a printer in the Chooser you should disable this extension.

MacinTalk 2

An older version of MacinTalk that operates on most Mac models, even a 68030 processor running at under 33 MHz. Suitable MacinTalk 2 voice files must also be present in the Voices folder.

MacLinkPlus for Easy Open 68K thng

This is for 680x0-based machines, and not to be confused with the OEM version, MacLinkPlus for ClarisWorks 68K, as supplied with ClarisWorks 5. The latter shouldn’t be enabled at the same time as MacLinkPlus for Easy Open or MacLinkPlus for Easy Open 68K.

Mailbox Extension fext

Provides a desktop mailbox for PowerTalk.

MathLib shlb

Provides fast number-crunching for PowerPC-native applications on a PowerPC.

Memory Manager shlb

Actually only manages memory for Apple’s defunct OpenDoc system.

Modem LinkTool Personal ldev

Used to establish a modem connection for Apple Remote Access (ARA) software.

N-Up Printing pext

A printing extension that appears in the Printing menu when using QuickDraw GX. It lets you print up to 16 pages on a single sheet of paper, each with an optional border.

Navigation Services

Provides improved Open and Save dialogue boxes in the Mac OS 7.5.5 or later. It’s only effective with applications that are designed to work with it. This feature is built into modern systems.

Network Extension fext

Lets you choose a type of network in the AppleTalk or Network control panel, and lets you choose File Sharing from the Finder. These functions are built into the System file in Mac OS 8.x.

ObjectSupportLib shlb

This library, also known as OSL, lets applications exchange standard Apple Events and provides the Open Scripting Architecture (OSA) for AppleScript. You should always use version 1.2, a fat library that’s suitable for both PowerPC and 680x0 computers. The CFM-68K Runtime Enabler must also be enabled for a 680x0 machine running Mac OS 7.x.

OpenDoc Libraries Folder

Contains special libraries that are used by OpenDoc.

OpenTpt Modem 68K libr

OpenTpt Remote Access 68K libr

These files perform similar functions to other files that lack the 68 K suffix. They should not be installed on a PowerPC since the machine will then emulate a 680x0 model and run slowly.

PC Card Extension fext

Enables the PC Card slots provided in some PowerBook models. The functions of this extension are built into the System file in Mac OS 8.x.

PC Card Modem Extension INIT

For using a PC Card Modem fitted into a slot in a PowerBook.

PowerBook 3400/G3 Ethernet ndrv

For an Ethernet expansion card installed in a PowerBook 3400 or PowerBook G3.

PowerBook 3400/G3 Modem ndrv

For a combined Ethernet/Modem expansion card in a PowerBook 3400 or PowerBook G3.

PowerBook Ethernet (PCI) ndrv

For an Ethernet card installed in a PCI slot in a PowerBook 3400 or PowerBook G3.

PowerBook Monitors Extension INIT

Adds options to the Monitors control panel for a PowerBook’s built-in video card. Works with VGA at 60 Hz and SVGA at 56 Hz.

PowerBook ZoomedVideo thng

For a ZoomedVideo PC card fitted into a PowerBook computer. Such a card provides a Zoomed Video port, as required for running a video conference.

PowerPC Monitors Extension INIT

Adds features to the Monitors & Sound control panel that accommodate an AudioVision 14" monitor connected a PowerPC machine. This extension supports 75 Hz greyscale monitors, RGB, S-Video or composite video connections, NTSC or PAL video and optional flicker reduction.

PowerTalk Extension INIT

PowerTalk Manager appe

For PowerTalk, a system that’s incompatible with Mac OS 8.x.

PPP mdev

A freeware mdev extension that works in conjunction with the Config PPP panel as part of the Apple Internet Connection Kit (AICK). When selected in the TCP/IP panel it provides MacPPP dial-up access to the Internet. To use the Open Transport PPP (OT/PPP) dialler mechanism built into Mac OS 8.x, you must remove this extension together with Config PPP. The Remote Access (or PPP) and Modem panels must then be enabled and set up as required.

Printer Share GX appe

Similar to the Printer Share extension, but designed for use with QuickDraw GX, the enhanced graphics system that’s incompatible with Mac OS 8.x.

Quadra AV Monitors Extension INIT

Adds options to the Monitors control panel for a Quadra AV or Centris AV machine with a built-in video card. It supports a Macintosh 16" or 21" Colour Display with RGB, S-Video or composite video connections. Both NTSC or PAL video standards are accommodated with optional flicker reduction. These computers are incompatible with later versions of Mac OS 8.x.

Quadra Monitors Extension INIT

Adds options to the Monitors control panel for a Quadra or Centris machine with a built-in video card. The extension supports 60, 67 and 75 Hz monitors, as well as VGA at 60 Hz, SVGA at 56 Hz, NTSC, NTSC Convolved, PAL and PAL Convolved. Computers of this type are incompatible with later versions of Mac OS 8.x.

QuickDraw™ GX fext

A mechanism that provides enhanced graphics and allows the use of GX fonts. Unfortunately, it uses around 1.2 MB of memory and is incompatible with Mac OS 8.x.

QuickDraw™ GX Enabler shlb

A library that’s used by the GXGraphics extension.

QuickDraw™ GX Helper INIT

Lets you quickly disable QuickDraw GX from the Apple menu when using an application incompatible with QuickDraw GX.

QuickTimeVRLib shlb

For viewing virtual reality (VR) images. Also requires the QuickTime VR extension. In modern versions of the system this library is built into the QuickTime VR file itself.

Scripting Additions Folder

Contains files to extend the abilities of AppleScript. In Mac OS 8.x and Mac OS 9.x this folder is inside the System Folder.

Serial Port Arbitrator LTMC

Used by older versions of Apple Remote Access (ARA) to sort out which software has access to a serial port that’s shared by ARA and another modem application, such as a fax program. Some applications of this type may object to the extension, in which case you’ll have to disable it.


Improves serial port operation on some computers but not required for Mac OS 7.5.3 or higher.

Shortcuts help

A special Apple Guide file that shows shortcuts in the Finder’s Help menu.

SoundInputCS4236 ndrv

SoundOutputCS4236 thng

Presumably used for sound input and output hardware of a specific type.

SR Monitor

Speech recognition monitoring software used with older versions of Speech Recognition, allowing the machine to listen to commands and to execute scripts contained in the Speakable Items folder.

Stationery uspt

A paper type for QuickDraw GX.

System Speech Rules

Accommodates language dialects when an older version Speech Recognition is enabled.

Thread Manager INIT

Gives the system a limited multi-tasking ability. This is built into the System file in Mac OS 8.x.

TokenTalk Phase 2 adev

TokenTalk Prep ttpp

Required if you are connected to a TokenTalk network.

Trackpad Climate Control INIT

Fixes a problem with the trackpad used in some PowerBook models. This function is built into the System file in Mac OS 8.x.

WorldScript™ I scri

WorldScript™ II scri

Necessary if you want to use a software language kit. WorldScript™ II is only required for language that use double-byte characters, such as Chinese, Japanese or Korean.

WorldScript™ Power Adapter scri

For native operation of WorldScript on a PowerPC-based machine. This function is built into the System file in Mac OS 8.x.

Other Outdated Files

There are numerous other outdated files. For example, all of the printer drivers (pdvr) provided with QuickDraw GX are obsolete since this system is incompatible with Mac OS 8.x. These drivers have similar names to normal printer extensions but carry a GX suffix.

The following library files, employed by a 680x0-based machine running Mac OS 7.x with the CFM-68K Runtime Enabler, are also outdated:-













In addition, the extensions shown in the following list aren’t provided with Mac OS 7.6 and are apparently no longer required. Most other files containing the words Enabler, Fix, Patch, Tuner, Update or Updater in their filenames are also redundant, unless contained in a later System Update. For full details you should refer to the InformINIT (D E Frakes).

950 Color Additions

Apple Event Manager

AppleTalk Service (PowerTalk)

AV Setup


External CD Sound

File System Manager

Macintosh Drag & Drop


Mount IDE Drive

Open Tpt ATalk 68K Library

Open Tpt Inet 68K Library

Open Transport 68K Library


PowerPC Interupt Extension

SCSI Manager

Serial DMA




Thread Manager

Libraries in Detail

Most Mac users had not heard of a shared library or dynamically loaded library (DLL) until the arrival of Apple’s PowerPC-based machines. Although different kinds of DLLs are use in the computing world, including those used by Microsoft’s Shared Code Manager, this section only considers those used with Apple’s Shared Library Manager (ASLM).

Most libraries contain one or more fragments of native code, designed for high-speed operation on a PowerPC-based computer. These are loaded into memory by the Code Fragment Manager (CFM), part of the system on a PowerPC.

Each fragment provides an application programming interface (API) that can be used by other applications, avoiding extra code within each application. Each library is loaded as required, meaning that unused libraries don’t consume your valuable memory. The code that makes up a library is stored in a specific library file or within another document, which is often inside the System Folder.

Embedded Libraries

Some libraries that are used by the Mac OS are embedded in the System file itself or in an extension. For example, the modern QuickTimeLib library is in the QuickTime PowerPlug extension file whilst SpeechLib is in the Speech extension file.

If such an extension is disabled you may see a dialogue that reports the missing library as if it were a missing file. Worse still, there’s no easy way of finding out which files contain which library! Of course, it would help if applications didn’t give such confusing messages. Unfortunately, Apple have a habit of moving libraries from documents and embedding them into files at the next revision of the system. So from the application developers point of view a vague message is unavoidable.

Library Files

Libraries are often supplied as separate documents whose contents can be used by the system, the Finder or any other application that needs it. These library files have a type code of shlb, filenames that often end in Lib and are often be found in the Extensions folder. However, a library that’s only used by one application can also be placed in the same folder as the application itself.

A library file contains one or more cfrg resources with the code itself kept in the file’s data fork, in the same way as in a PowerPC application file. The library itself is usually in PowerPC form although some files contain only 680x0 code or both kinds of code (see below).

Some files contain a glue library that allows native code in a PowerPC-compatible application to use 680x0 code. This form of library file may, or may not, have the word Glue in its filename.

If you install a new document, containing a library that’s already embedded in a standard file (such as the System file or another extension), this separate library file overrides the original. This can be an advantage but can cause problems. For example, a non-standard library file such as LibMotoSh can replace a similar library in the System, improving performance, but at the risk of complications. Worse still, an application installer may provide libraries that are older than the originals.

Open Transport Library Files

A special type of library file is used for Open Transport, the modern version of AppleTalk software used for running a Mac computer network. These files have a type code of libr, filenames that sometimes end in Library and are invariably found in the Extensions folder

Each contains the code within its resource fork, which is loaded, unloaded or shared by the Shared Library Manager. Although most files contain PowerPC code, others contain only 680x0 code or both kinds of code (see below).

680x0 Libraries

Although library files were primarily intended for use on a PowerPC, there are some libraries that accommodate programming code for older 680x0-based machines. Such files are often identified by a filename prefix of Nu or a suffix of 68K or .slb. If you encounter a fat library, containing both PowerPC and 680x0 code, you may find that it doesn’t have such a distinctive filename.

To use any type of library that contains 680x0 code on a 680x0-based machine with Mac OS 7.x you must have the CFM-68K Runtime Enabler extension. This partially emulates the Code Fragment Manager in a PowerPC but is of no use on a PowerPC since the CFM is already part of its system.

Versions of Mac OS 8.x designed for 68040-based machines actually incorporate older libraries and the CFM-68K Runtime Enabler into the System file itself, making the separate files unnecessary.

Fortunately, any PowerPC library that’s present on a 680x0-based machine is simply ignored. On the other hand, an unnecessary 680x0 library on a PowerPC-based computer can slow down the machine, since the machine may try to use the offending library to emulate a 680x0 computer.

©Ray White 2004.