Customize the way a web page displays or behaves, by using small bits of JavaScript.

Greasemonkey promo image
What is Greasemonkey?

Greasemonkey is an advanced Firefox add-on that provides users the opportunity to personalize how a webpage displays or functions. Through scripting small JavaScript snippets, users can modify internet pages, create personalized site scripts, or use existing ones. It also provides a platform for troubleshooting and script hosting.

Rating: 4.17 (1,229)
Version: 4.12.0 (Last updated: 2023-12-18)
Creation date: 2005-05-20
Weekly download count: 3,351
Firefox on Android: Yes
Risk impact: High risk impact
Risk likelihood: Moderate risk likelihood
Manifest version: 2
  • <all_urls>
  • clipboardWrite
  • cookies
  • downloads
  • notifications
  • storage
  • tabs
  • unlimitedStorage
  • webNavigation
  • webRequest
  • See more
Size: 630.29K
URLs: Website
Stats date:

Other platforms

Not available on Chrome
Not available on Edge
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Allows you to customize the way a web page displays or behaves, by using small bits of JavaScript.

You can write your own scripts, too. Check out to get started. Many scripts already exist, probably ones to enhance your favorite sites. Find them at .

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User reviews
User reviews summary
These summaries are automatically generated weekly using AI based on recent user reviews. Firefox Browser Add-ons does not verify user reviews, so some user reviews may be inaccurate, spammy, or outdated.
  • 非常实用 (Very practical/useful)
  • Lack of updates for 3 years
  • Incompatibility with current versions of Firefox
  • Broken UI in Firefox 119.0 (64-bit)
  • Scripts not working properly when compared to other similar extensions
Most mentioned
  • Outdated/no recent updates
  • Incompatibility issues with new Firefox versions
  • Comparison with Tampermonkey and Violentmonkey
View all user reviews
Risk impact

Greasemonkey 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 Greasemonkey if you trust the publisher.

Risk likelihood

Greasemonkey is probably trust-worthy. Prefer other publishers if available. Exercise caution when installing this add-on.

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