Grease Monkey is derived from It allows users to install scripts that make it easier to change most HTML-based web pages directly on the client side. With Greasemonkey scripts reside in the browser, each time with the purpose of the page opened and automatically make changes, so that the user running the script impressed by its fixed convenience.

Greasemonkey abbreviated as GM The function of Greasemonkey, commonly known as "grease monkey" in Chinese, is to add new functions to web pages, fix web bugs, combine data from different web pages, or other functions that are not as well prepared. Well-written Greasemonkey scripts can even make its output seamlessly integrated with the page being modified, as if it were part of the original Web page.

Most Greasemonkey user scripts are written in-house, using JavaScript code specific to a site, and manipulating web content through the Document Object Model (DOM) interface. userscripts.org maintains a Greasemonkey database. This database describes which web pages correspond to which scripts. However, with the closure of the userscripts site, some developers have opened their own sites to publish scripts, and Greasemonkey officially set up a list of third-party scripts on the wiki site.

Many technical analysts warned that the use of Greasemonkey too much, for example, may allow some advertising sites blocked, blocking web ads, replacing the original advertiser ads, increasing site spam traffic, interactive performance is reduced, so no interaction with the original site developers and write the Greasemonkey script may work at a time, but ultimately not a long-term solution. However, these problems are from the technical level to illustrate, for the user is still a great aspect of the user's experience on the Internet effect.