A userscript (or user script) is a program, usually written in JavaScript, for modifying web pages[1] to augment browsing.
The Presto-based Opera-supported userscripts (referred to as User JavaScript[3]) are placed in a designated directory.
Historically (circa 2005–2011) userscripts.org, created by American programmer Jesse Andrews, was the largest such repository for userscripts.
Also available is Greasy Fork, a repository largely developed and maintained by Canadian programmer Jason Barnabe.
[9][non-primary source needed] Users of the Greasemonkey[10] and Tampermonkey[11] extensions may choose to install .user.js scripts from any location.