usi (User|Unified Script Injector)

usi (User|Unified Script Injector)

use UserScripts on your Firefox for Android with usi!

usi (User|Unified Script Injector) promo image
What is usi (User|Unified Script Injector)?

usi (User|Unified Script Injector) is a Firefox add-on that allows you to use user scripts on Firefox for Android. It supports experimental Greasemonkey functions, enables easy addition of user scripts through a textbox or URL, and allows the use of jQuery in user scripts.

Users: 73 ▲ 3
Rating: 3.88 (25)
Version: 0.5.16 (Last updated: 2020-11-25)
Creation date: 2015-03-25
Weekly download count: 1
Firefox on Android: Yes
Risk impact: High risk impact
Risk likelihood: Low risk likelihood
Manifest version: 2
  • <all_urls>
  • clipboardRead
  • clipboardWrite
  • notifications
  • storage
  • unlimitedStorage
  • tabs
  • webNavigation
Size: 1.04M
URLs: Website
Stats date:

Other platforms

Not available on Chrome
Not available on Edge
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Now you can use your Userscripts on your Firefox for Android, too.

Firefox 57+ Please install USI in version 0.5.1.x for usage in Firefox 57 and above.

If you find any Bugs, please create an issue at

  • experimental Greasemonkey functions (GM_getValue,GM_setValue,GM_deleteValue,GM_listValues,GM_setClipboard,GM_openInTab,GM_log,GM_addStyle)
  • you can add a Userscript through a simple Textbox on your device, or you load it by an URL
  • if you open a Userscript in it's own tab with an ".user.js" ending, USI will ask if you want to import this Userscript
  • you can use jQuery in your Userscripts (@include-jquery)
Note: This Addon is still an alpha version, many things will not work properly.

Userscripts written for Greasemonkey won't run sometimes, because of the handling for @run-at defined in the meta block. Try to change it from "document-start" to "document-ready" if some Userscripts does not run. For more Information about this topic, take a look on this page where contentScriptWhen is explained (

User reviews
Can't install scripts from Greasy Fork and when I install them manually they don't work
by Gersonzao, 2022-10-01
View all user reviews
Risk impact

usi (User|Unified Script Injector) is risky to use as it requires a number of sensitive permissions that can potentially harm your browser and steal your data. Exercise caution when installing this add-on. Review carefully before installing. We recommend that you only install usi (User|Unified Script Injector) if you trust the publisher.

Risk likelihood

usi (User|Unified Script Injector) has earned a fairly good reputation and likely can be trusted.

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