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 by USI. This add-on has 103 daily active users and an average user rating of 3.88. The latest version, 0.5.16, was updated 2 years ago.

Stats date:
Users: 103 ▲ 1
Rating: 3.88 (25)
Version: 0.5.16 (Last updated: 2020-11-25)
Creation date: 2015-03-25
Weekly download count: NaN
Firefox on Android: Yes
Manifest version: 2
  • <all_urls>
  • clipboardRead
  • clipboardWrite
  • notifications
  • storage
  • unlimitedStorage
  • tabs
  • webNavigation
Size: 1.04M
URLs: Website
Risk impact: Very high risk impact
Risk likelihood: Low risk likelihood
Found a bug?

Other platforms

Not available on Chrome
Not available on Edge
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 (
Risk impact

usi (User|Unified Script Injector) requires a lot of risky permissions and is not safe to use. Avoid installing this add-on unless you absolutely trust this publisher.

Risk impact measures the level of extra permissions an extension has access to. A low risk impact extension cannot do much harms, whereas a high risk impact extension can do a lot of damage like stealing your password, bypass your security settings, and access your personal data. High risk impact extensions are not necessarily malicious. However, if they do turn malicious, they can be very harmful.

Risk likelihood

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

Risk likelihood measures the probability that a Firefox add-on may turn malicious. This is determined by the publisher and the Firefox add-on reputation on Firefox Browser Add-ons, the amount of time the Firefox add-on has been around, and other signals about the Firefox add-on. Our algorithms are not perfect, and are subject to change as we discover new ways to detect malicious extensions. We recommend that you always exercise caution when installing a Firefox add-on, especially ones with higher risk impact and/or higher risk likelihood.

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