Inside The System Folder

What is an Extension? An Extension is a small file that changes how your computer operates. Unlike a Control Panel, you typically do not have any direct interaction with an Extension. An Extension makes the appropriate changes when you start your computer and remains active until you shutdown your computer.
Depending on the type of computer you have, the contents of your Extensions folder may vary. You might also have Extensions that were added by third-party applications.

To disable an Extension, simply take it out of the Extension Folder and put it in a folder called Extensions (disabled), this can be placed in the System Folder, don't worry, no Extension will be loaded from this particular folder. You can also use the Extension Manager Control Panel to do the same thing.
Other types of Extensions are actually Libraries, these are often used by many applications or system components. It is usually a good idea not to turn off libraries, otherwise it may cause some programs not to load up. Some of the more common ones are listed in the Libraries link below.

Below, I've listed some miscellaneous Extensions that the installer placed in your system that you may not need, see Other Extensions for further details.

EM Extension
Works with the Extensions Manager Control Panel, which lets you specify which Extensions are turned on when you start your computer.

About Apple Guide
Provides information about how to use Apple's on-screen help system.

ADSP
AppleTalk Data Stream Protocol, provides networking protocol under pre-7.0 systems. More specifically, it provided data flow and full duplex data delivery over a network. However, in order for the benefits to be realised, both Macs had to be running this Extension.

AppleCD Audio Player Guide
Provides step-by-step instructions for using the AppleCD Audio Player.

Apple CD-ROM
Enables your computer to use an Apple CD-ROM drive.

Apple Color SW Pro CMM
Contains colour-matching information used by ColorSync 2.0 to maintain consistent colour between documents.

AppleGuide
Enables your computer to use Apple's on-screen help system. You can access Macintosh Guide from the ? menu (the help menu is on the right hand side of the menu-bar), whilst in the Finder. This feature can only be found in Systems 7.5 to 8.1. Appleguide file 'additions':
AppleVision Guide Additions, AV Guide Additions, Energy Saver Guide Additions, Monitors & Sound Guide Additions, Network Guide Additions, Open Transport Guide Additions, Speech Guide Additions, Video Guide Additions
These add step-by-step instructions for using features specific to a program, MacOS, or Control Panel.

Apple Multimedia Tuner
Enhances QuickTime 2.0 and Sound Manager 3.0. Once you upgrade to QuickTime 2.1 and Sound Manager 3.1, or System 7.5.3/Update 2.0, this is no longer necessary.

Apple Photo Access
Part of the CD-ROM software, and is needed for viewing Kodak PhotoCDs.

AppleScript
Enables automation of repetitive tasks in applications that support it. Some applications, such as Apple on-screen help, require AppleScript to work.

AppleShare
Gives you access to shared disks on the network. Systems 7.6 through to 8.1 uses a later version of AppleShare that is incompatible with ShapeShifter up to v3.10.

Audio CD Access
Lets you play audio CDs on your internal or external CD-ROM drive. Requires the AppleCD Audio Player or equivalent application to control the audio CD.

Clipping Extension
Lets you use the drag-and-drop feature to create clipping files on your desktop.

Color Picker
Creates a standard colour selection interface for all applications.

Color SW 2000 Series CMM
Colour-matching information used by ColorSync to maintain consistent colour between documents printed on a Color StyleWriter 2000 series printer and other colour devices.

ColorSync
Matches colours on your display with the closest matching colours on your printers, scanners, and other devices.

Desktop Printer Extension / Desktop Printer Spooler / Desktop PrintMonitor
All three of these files are necessary for the desktop printing feature to work. (With desktop printing, you can print documents by dragging their icons to printer icons.)

Dragging Enabler / Drag Enabler
Provides Drag Manager support under System 7.0 and 7.1. When used with the Macintosh Drag and Drop Extension, provides inter-application drag and drop support under System 7.1. Integrated into the Finder under System 7 Pro and later.

Energy Saver Extension
Used in conjunction with the Energy Saver Control Panel. Sends the Mac to sleep.

Ethertalk Phase 2
Lets you connect your computer to an Ethernet network.

File Sharing Extension
Enables your computer to share files and folders with other computers on your network.

Find File Extension
Lets you search for files and view the results in a single window. If you turn off this Extension and choose Find from the File menu, you'll get the System 7.1 Find dialogue box instead of Find File.

Finder Help
Provides Balloon Help support for the Finder.

Finder Scripting Extension
Allows you to use AppleScript to automate tasks in the Finder.

Foreign File Access
Enables your computer to work with CD-ROM discs whose contents don't use the standard Mac OS file system (for example, ISO 9660 or High Sierra formats).

Global Guide Files folder
Contains files used by the on-screen help system. Some of these files may be used to provide help more than one application.

High Sierra File Access
Part of the CD-ROM software that lets you view CDs with High Sierra file systems.

Installer Cleanup
This is put in the System Folder after a OS is installed. All it does is to make sure that the installation process was successful and that everything was installed in the proper place. You must allow it to load on the next restart so that it can take care of any files that were left behind after the installation. It should then disappear.

ISO 9660 File Access
Part of the CD-ROM software that lets you view CDs with ISO 9660 file systems.

LaserWriter 8
(Version 8.x) A PostScript level II print driver that enables your computer to print documents on a PostScript printer connected to an AppleTalk network.

Mac OS Guide
Contains step-by-step instructions for working in the Finder. You access Mac OS Guide from the Guide (question mark) menu when the Finder is active.

MacinTalk 3
Lets your computer read text documents in human-like voices.

MacinTalk Pro
Lets your computer read text documents in human-like voices. Older computers (with 68030 or 020 processors) should use MacinTalk 3 instead.

Macintosh Drag / Drag&Drop Extension
Provides Drag and Drop support under Systems 7.0.x and 7.1.x. These two files are still installed by numerous software packages, such as Now Utilities and ccMail, for universal compatibility, but are not needed under System 7.5 and later.

MacIPX AppleTalk / MacIPX TCP/IP / MacIPX Token Rink
These are network drivers which support the MacIPX protocol over the respective network type (ie. AppleTalk, TCP/IP or Token Ring).

MacTCP Token Ring Extension
Allows you to use the TCP/IP protocol over a Token Ring network.

Mailbox Extension
Supports your PowerTalk mailbox. Enables the Mailbox icon to appear on your desktop.

My Speech Macros
Supports the Speech Macro Editor.

Network Extension
Lets you set Personal File Sharing from the Finder.

Printer Descriptions
This folder contains printer description files (PDFs) for any make of printer.

Printer Driver Extensions
These are Extensions which allow access/connection to various types of networks, services, printers, etc. using the Chooser. They do not take up any RAM when the System has booted-up. Most of these (99.9%) can be deleted out of the Extensions folder, it is very unlikely you won't have these printers.
AppleTalk ImageWriter
Color SW 1500 (SW=StyleWriter)
Color SW 2200
Color SW 2400
Color SW 2400
Color SW 2500
Color SW Pro
Color SW Pro GX (GX=QuickDraw GX compatible)
ImageWriter
ImageWriter GX
ImageWriter LQ GX
Laserwriter 8.x (General purpose postscript II compatible printer driver)
LaserWriter 300 & LaserWriter 300/LS
LaserWriter 300 GX
LaserWriter GX
LaserWriter IISC GX
LW 300/LS GX
LW Select 310
Personal LaserWriter SC
Portable StyleWriter
StyleWriter 1200
StyleWriter GX

Printer Share / Printer Share GX
Provides the ability to share non-network printers (for example, the StyleWriter II) across a network.

PrintMonitor
This application allows you spool your print jobs to any printer.

PowerTalk Extension
Supports PowerTalk services. Includes information used by the PowerTalk key chain.

PowerTalk Manager
Manages your PowerTalk mailbox and services.

QuickDraw GX
QuickDraw GX is a specialist (no longer supported) printing system. Note that if this Extension is installed, you must have GX-compatible printer drivers. If you have this Extension installed, non-GX drivers will not even show up in the Chooser.

Printer Description
This folder contains Postscript2 printer description files or PPDs, and includes PPDs for most of Apple's own printers.

QuickTime
Provides built-in multimedia support for applications.

QuickTime PowerPlug
Provides native support of QuickTime for PowerPC-based computers when used in combination with QuickTime 2.x onwards.

QuickTime Musical Instruments
Supports 30 Roland Standard MIDI sound samples that can be accessed by QuickTime applications with no additional MIDI equipment.

Scripting Additions
Extends the AppleScript language with special features, such as finding the date or time of day. With scripting additions installed, AppleScript acts as if these features are part of the language. Scripting additions are required only when a script uses them.

Serial (Built-In)
Used by Open Transport to allow access to the built-in serial port on your computer.

Shared Library Manager
Provides native support for Open Transport.

Shortcuts
Explains common keyboard equivalents and other shortcuts to use in the Finder. You can access Shortcuts in the Guide (question mark) menu when the Finder is active.

SimpleText Guide
Provides step-by-step instructions for using SimpleText. You can access the SimpleText Guide from the Guide (question mark) menu, after you open SimpleText.

SOMobjects for Mac OS
Used by OpenDoc.

Speech Manager
Provides text-to-speech capabilities.

SR Monitor
Used to monitor and interpret speech.

Startup Tuner
Ensures correctly starting up from the disk selected in the Startup Disk Control Panel.

System 7 Tuner
For System 7.0, and comes on the System Tune-Up disk. It provided better memory management for the initial release of System 7.

SystemAV
Used for audio-video input. Required by the Monitors & Sound Control Panel.

System Speech Rules
Supports voices and speech dialects.

Thread Manager
Thread Manager is an addition to the Macintosh Toolbox that enables concurrent programming for real multi-tasking within an application. Supports cooperative and pre-emptive threads of execution at the application level, but not at the system level. It has been incorporated into System 7.5 onwards.

TokenTalk Phase 2
Used by the Apple Token Ring card.

TokenTalk Prep
Provides driver support for TokenTalk Phase II.

Tutorial Items
Provides instructions for learning basic skills on your computer. You can access the tutorial from the Guide (question mark) menu when the Finder is active.

Video Out Default (PAL)
Used by the Apple Video Player. On the standard U.S. System, the default video-out for the Apple Video Player is NTSC. Outside of the US, the standard video format is PAL - this Extension changes the Apple Video Player default to PAL.

Video Startup
Used by the Apple Video Player.

Voices folder
Contains voices for use by Speech/ PlainTalk/ Text-to-Speech.

WorldScript Power Adapter
Supports language kit software on PowerPC-based computers. However, computers that use the Roman alphabet (English and French, for example), can still take advantage of performance and stability enhancements provided by the WorldScript Power Adapter.

These will probably not be installed on later System OSs, eg. 7.5 to 8.1, although it depends entirely on the MacOS you are running, the processor, and any added hardware, such as; a CD-ROM drive, Ethernet, SCSI etc. 99% of these will not apply to you, so you can safely bin them.

A/ROSE
Allows communication between your computer's main logic board and NuBus cards that run the Apple Real-Time Operating System. Examples of such NuBus cards include the Apple Token Ring 4.16 NB card and the Apple Serial NB card.

ADBReInit
ADB is a port on the Mac, which you use to plug in the keyboard and mouse. The ADBReInit Extension prevents memory from being moved at interrupt time, which could cause the some PowerBook and Quadra models to hang or crash.

Appleguide Additions
PB 500 Upgrade Guide Additions, PB 190 Upgrade Guide Additions, PB 2300 Upgrade Guide Additions, PB 5300 Upgrade Guide Additions, PowerBook Guide Additions
Adds step-by-step instructions for using features specific to Powerbook Macs.

Apple Built-In Ethernet / Apple Ethernet NB
A driver for the built-in Ethernet port on Nubus-based Macs.

Apple Event Manager
Allows applications (including the Finder) to send commands to other applications (again, including the Finder). For example, in InformINIT, when you click on the little "IE" and "NN" buttons, InformINIT sends an Apple Event to Netscape telling it to go to the URL listed. This file is incorporated into the AppleScript Extension with System 7.5 and above.

AppleTalk ImageWriter
Enables your computer to print documents on a networked ImageWriter II.

AppleVision
Only used for support of AppleVision monitors only.

AudioVision
Part of the AudioVision 14 inch monitor software package. Only needed on
pre-7.5 systems.

Assistant Toolbox
This is the base Extension for AutoRemounter. AutoRemounter works on Macintosh PowerBook computers and allows file synchronisation, battery management, and easy mobile computing. It also provides support for a persistent RAM disk and deferred printing. This Extension may conflict with the LaserWriter Select 310 printer software to block printing. A solution is to turn off background printing in the Chooser.

At Ease 7.5 Layer Patch
Fixes a crash when using At Ease, and the Show Desktop box is unchecked in the General Controls Control Panel.

At Ease Startup
Forces your Mac to start up with the At Ease instead of the standard Mac Finder.

AV Setup
Used to control AppleVision displays.

Caps Lock
Provides a visual indication of the state of the Caps Lock key on a Macintosh PowerBook. When Caps Lock is turned on, an Up arrow appears in the menu bar next to the Guide "?" menu. (Not needed on Macintosh PowerBook 500 series computers.)

CFM Update
Installed by older versions of QuickDraw 3D. CFM stands for Code Fragment Manager.

DAL
Enables network activity using Data Access Language, formerly called CL/1. Data Access Language is Apple's client/server protocol for remote data access and is based on ANSI standard SQL (Structured Query Language). DAL is optimised to provide decision-support applications with uniform access to data, regardless of the different brands of databases, the different host platforms, or the different types of networks.

Desktop Printer Menu
Creates a menu bar which allows you to change to a different printer without having to use the Chooser.

Display Enable
Provides multiscan/multisync support, especially for AppleVision monitors. Adds functionality to Energy Saver, and to the Monitors control strip module by allowing you to switch resolutions on-the-fly.

DoubleTrouble
For use under pre-System 7.5 systems. When using a debugging utility, the DoubleTrouble Extension will break into the debugger to alert you whenever the code in a project attempts to free a "handle" that has already been freed. An unsupported Apple Extension. NOTE: do not use this Extension with System 7.5 or later. It is intended only for pre-7.5 use.

Ethernet (Built-In)
Used by Open Transport to allow access to the built-in Ethernet port on on PCI Macs. Not to be confused with the Apple Built-In Ethernet Extension.

EthertalkPrep
On older systems, worked with Ethertalk Phase 2 to establish and maintain Ethernet connections. No longer needed under 7.5.3.

FontSize Patch
Fixes problems with font corruption when using the Asian language kits under System 7.5.3 and later.

Frontmost Extension
Frontmost comes with the full AppleScript commercial product, it allows you to create sophisticated user interfaces for AppleScript applications. It also acts as a run-time assistant for projects saved as miniature applications.

GetInfo
For use only under System 7.0. Provides extra information about files which depend on other files by modifying the Get Info... box. Only works with applications that use QuickTime.

Graphics Accelerator
Provides video acceleration for PCI Macs using an ATI video card.

Hardware System Update 1.0/2.0/3.0
System 7.1 Updates. Provided numerous system-level improvements. This file was not designed for use on Performa models.
Version 2.0 adds further improvements and overall stability, while version 3.0 increases reliability and performance, even further. AV Systems already have these improvements in their ROMs.

IIci/IIsi Monitors
Describes the capabilities of the built-in video card for the Macintosh IIci and IIsi. If you remove this file, your computer can still use the video card and you can still select the number of colours displayed on your monitor, but monitor options (such as gamma settings) may not be available.

InLine Filter
Helps AppleScript and PlainTalk Speech Recognition work together. Allows Worldscript users to type scripts 'in-line' instead of to a separate text file.

Insomnia
Created for Apple PowerBooks to keep them from falling asleep.

LC Monitors Extension
Adds functionality to the Monitors Control Panel for LC series Macs.

Letterhead
Is part of the QuickDraw GX package, this Extension enables the Letterhead paper type option in the Page Setup window of all GX compatible applications.

LocalTalk DMA
Is part of the obscure System 7.5.3 Revision 2.1, this file fixes a bug with transferring files over LocalTalk on Performa 6400/180 and 6400/200 computers. This fix is included in the System 7.5.5 Update.

MIDI Manager
Enables Apple's MIDI Management system.

Modem Scripts
A folder which contains the modem descriptions/scripts used by OT/PPP and Apple Remote Access to communicate with your modem.

Mount IDE Drive
Allows Macs with IDE hard drives to mount these drives when the Mac is booted from another disk or device.

N-Up Printing
Part of the QuickDraw GX package, this Extension allows you to print more than one page on a single sheet of paper by dividing the page into smaller sections and reducing the printing size. Up to 16 pages can be printed on a single 8.5x11 sheet.

Network Launch Fix
On 68040 Macs, fixed a bug when launching applications over a network. Incorporated into system 7.5 and later.

PC Net Exchange
Works with the PC Exchange Control Panel to help Mac users share DOS/ Windows files over an AppleTalk network with users of the AppleShare Client for Windows software.

Printer Selector
Under LaserWriter 8.4 and above, this adds a menu of configured printers to your menu bar for quick printer switching.

ProDOS File System
Allowed pre-7.5 Macs to recognise ProDOS/Apple IIe disks. Incorporated into PC Exchange 2.0.2 and later, and is incompatible with System 7.5.x.

PowerBook Monitors Extension
Describes the PowerBook built-in display. If you remove this file, your computer can still use the PowerBook video card and you can still select the number of colours your screen can display, but certain options (such as gamma settings) may not be available.

PowerPC Monitors Extension
Supports Apple's AudioVision 14 monitor.

Quadra AV Monitors Extension
Describes the capabilities of the built-in video card for the Macintosh Quadra and Centris AV computers. If you remove this file, your computer can still use the video card and you can still select the number of colours displayed on your monitor, but monitor options, ie. Gamma settings, may not be available.

Quadra Monitors Extension
Describes the capabilities of the built-in video card for the Macintosh Quadra and Macintosh Centris computers. If you remove this file, your computer can still use the video card and you can still select the number of colours displayed on your monitor, but monitor options (such as gamma settings) may not be available.

Scanner
Is a driver for all Apple scanners (including 3rd party compatible scanners).

SCSI Manager
Version 4.3 is incorporated into the System under System 7.5.3 and later. On earlier systems, this is a SCSI driver upgrade Extension for all (real) Macintoshs, with in-built SCSI.

SCSI Update
Included with the AppleShare IP 5.0 beta. Updates the SCSI Manager to allow asynchronous access on machines that don't already support it, such as 680x0 machines and early PowerMacs. The new SCSI Manager is required for products such as the Advanced Driver Toolkit from Dantz for accessing Digital Linear Tapes from within Retrospect.

SerialDMA v2.02
Is a driver update for DMA chips for PPC and 68040 Macs. Serial DMA is now incorporated into the System file from System 7.5.3 onwards.

Sound Manager
Sound Manager 3.2 was incorporated into the System in System 7.5.3, and included asynchronous sound playback. Version 3.2.1 is part of the QuickTime 2.5 package and provides even better low-memory performance and better multi-channel sound via a new sound clock component. Sound Manager 3.2.1 is built into the System file under 7.6.

Startup Tuner
Part of the System 7.5.3 revision, fixes a problem with the Startup Disk Control Panel where the Mac (on selected models) may not startup from the selected disk. Not necessary for System 7.5.5 and later.

Stationary
Part of the QuickDraw GX package, this Extension enables the Stationary paper type option in the Page Setup.. window of compatible applications.

TokenTalk Phase 2
Driver used by the Apple Token Ring card and the Network/AppleTalk Control Panels.

Video Startup
Provides support for the Apple Video Player; needed to use the AVP.

WindowPicker
Older, unsupported utility which provides the ability to bring any open window to the front via a pop-up menu and/or arrow keys.

Shutdown Items enabler
Provides support for the Shutdown Items folder under System 7 Pro.