In computing, an accelerator is an additional unit of hardware to perform some function faster than is possible in software running on the normal CPU. Examples include graphics accelerators and floating-point accelerators . The term is outdated and has been replaced with more descriptive terms like video card or graphics card.

In computing, the term accelerator is also used for the shortcut key which produces the same effect as a pull-down menu entry, for example using CTRL-S instead of the menu "File" and the contained entry "Save".

In web programming , accelerator refers to a program, similar to an operating system cache but meant for website delivery, that is an intermediate between the web server and the scripting language that performs caching functions that aid in allowing web scripts to be delivered the requesting client faster than without the accelerator. The only drawback to this system is that if web scripts are constantly changed the cache needs to be emptied to ensure only the new versions of server scripts are sent to the client.

An accelerator is essential for large and constantly visited websites.

See also: Web cache