Plug-in (computing)

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Mozilla Firefox displaying a list of installed plug-ins

In computing, a plug-in (or plugin, add-in, addin, add-on, or addon) is a software component that adds a specific feature to an existing computer program. When a program supports plug-ins, it enables customization.[1]

A theme or skin is a preset package containing additional or changed graphical appearance details, achieved by the use of a graphical user interface (GUI) that can be applied to specific software and websites to suit the purpose, topic, or tastes of different users to customize the look and feel of a piece of computer software or an operating system front-end GUI (and window managers).

Purpose and examples[edit]

Applications support plug-ins for many reasons. Some of the main reasons include:

Types of applications and why they use plug-ins:


Example Plug-In Framework

The host application provides services which the plug-in can use, including a way for plug-ins to register themselves with the host application and a protocol for the exchange of data with plug-ins. Plug-ins depend on the services provided by the host application and do not usually work by themselves. Conversely, the host application operates independently of the plug-ins, making it possible for end-users to add and update plug-ins dynamically without needing to make changes to the host application.[11][12]

Programmers typically implement plug-in functionality using shared libraries, which get dynamically loaded at run time, installed in a place prescribed by the host application. HyperCard supported a similar facility, but more commonly included the plug-in code in the HyperCard documents (called stacks) themselves. Thus the HyperCard stack became a self-contained application in its own right, distributable as a single entity that end-users could run without the need for additional installation-steps. Programs may also implement plugins by loading a directory of simple script files written in a scripting language like Python or Lua.

Mozilla definition[edit]

In Mozilla Foundation definitions, the words "add-on", "extension" and "plug-in" are not synonyms. "Add-on" can refer to anything that extends the functions of a Mozilla application. Extensions comprise a subtype, albeit the most common and the most powerful one. Mozilla applications come with integrated add-on managers that, similar to package managers, install, update and manage extensions. The term, "plug-in", however, strictly refers to NPAPI-based web content renderers. Mozilla deprecated plug-ins for its products.[13] But UXP-based applications, like web browsers Pale Moon and Basilisk, keep supporting (NPAPI) plugins.[14][15][16]


Plug-ins appeared as early as the mid 1970s, when the EDT text editor running on the Unisys VS/9 operating system using the UNIVAC Series 90 mainframe computers provided the ability to run a program from the editor and to allow such a program to access the editor buffer, thus allowing an external program to access an edit session in memory.[17] The plug-in program could make calls to the editor to have it perform text-editing services upon the buffer that the editor shared with the plug-in. The Waterloo Fortran compiler used this feature to allow interactive compilation of Fortran programs edited by EDT.

Very early PC software applications to incorporate plug-in functionality included HyperCard and QuarkXPress on the Macintosh, both released in 1987. In 1988, Silicon Beach Software included plug-in functionality in Digital Darkroom and SuperPaint, and Ed Bomke coined the term plug-in.[citation needed]

See also[edit]


  1. ^ Sterne, Jonathan. "Plug-in | software". Encyclopedia Britannica. Retrieved 2021-02-05.
  2. ^ "PCSX2 - The Playstation 2 emulator - Plugins". Retrieved 2018-06-10.
  3. ^ Bernert, Pete. "Pete's PSX GPU plugins". Retrieved 2018-06-10.
  4. ^ Team, Demul. "DEMUL - Sega Dreamcast Emulator for Windows". Retrieved 2018-06-10.
  5. ^ "Android Emulator Plugin - Jenkins - Jenkins Wiki". Retrieved 2018-06-10.
  6. ^ "KDE/dolphin-plugins". GitHub. Retrieved 2018-06-10.
  7. ^ "OpenEmu/SNES9x-Core". GitHub. Retrieved 2018-06-10.
  8. ^ "Recommended N64 Plugins". Emulation General Wiki. Retrieved 2018-06-10.
  9. ^ "Playstation plugins & utilities!". Retrieved 2018-06-10.
  10. ^ "PS3 Homebrew Apps / Plugins / Emulators | PSX-Place". Retrieved 2018-06-10.
  11. ^ Mozilla Firefox plugins – Description of the difference between Mozilla Firefox plugins and extensions under the general term add-on.
  12. ^ Wordpress Plug-in API – Description of the Wordpress Plug-in architecture.
  13. ^ Paul, Ian. "Firefox will stop supporting plugins by end of 2016, following Chrome's lead". PCWorld. IDG. Retrieved 20 October 2016.
  14. ^ "Pale Moon: Technical Details - Features". Pale Moon. Retrieved 2020-06-06.
  15. ^ "Basilisk: Features". Basilisk. Retrieved 2020-06-06.
  16. ^ "Re: Remember: Plugins are outdated". Pale Moon Forums. Retrieved 2020-06-06.