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Browser Extensions · head to head

Greasemonkey vs React Developer Tools

Greasemonkey logo

Greasemonkey

Browser Extensions

The original userscript manager, for Firefox

From
Free
Rated
-
Full reviewWebsite
React Developer Tools logo

React Developer Tools

Browser Extensions

Debug React applications in your browser

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Greasemonkey firefox only. There is no Chrome, Edge or Safari build and there never has been.; React Developer Tools react Developer Tools is only available as a Chrome browser extension. No support for other browsers mentioned.
  • They diverge on capability: Greasemonkey covers Userscript execution, React Developer Tools covers Component inspection.
  • Prices and features above were last checked on 15 September 2026.

Where they differ

Only the attributes on which Greasemonkey and React Developer Tools actually diverge.

Attributes where Greasemonkey and React Developer Tools differ
AttributeGreasemonkeyReact Developer Tools
Pricing modelopen-sourcefree
PlatformsFirefoxChrome, Firefox, Edge
FoundedUnknown2004

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Browser Extensions).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Greasemonkey

  • Userscript execution
  • Built-in script editor
  • GM. API
  • @resource support
  • Script localisation
  • Firefox for Android

Only in React Developer Tools

  • Component inspection
  • Props/State viewing
  • Performance profiler
  • Hooks debugging
  • Chrome support
  • Firefox support
  • Edge support

What people use each for

The jobs each tool is most often brought in to do.

Greasemonkey

  • Restyling or de-cluttering a site you use dailynot React Developer Tools
  • Automating a repetitive action on a web applicationnot React Developer Tools
  • Adding a missing feature to a site you do not controlnot React Developer Tools
  • Running userscripts on Firefox for Androidnot React Developer Tools
  • Writing and testing your own scripts in the browsernot React Developer Tools

React Developer Tools

  • Debugging React components during developmentnot Greasemonkey
  • Inspecting component state and propsnot Greasemonkey
  • Performance profiling of React applicationsnot Greasemonkey

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Greasemonkey

  • Firefox only. There is no Chrome, Edge or Safari build and there never has been.
  • Its API diverged from the Tampermonkey conventions most shared scripts are written against, so a script from a sharing site may need adjusting to run.
  • The dashboard is plainer than Tampermonkey's, with no diff view when a script updates itself.
  • No cloud sync of the kind Tampermonkey and Violentmonkey offer; moving machines means exporting.
  • A userscript manager can read and rewrite every page you visit, so the security of the arrangement depends entirely on the scripts you choose to install.

React Developer Tools

  • React Developer Tools is only available as a Chrome browser extension. No support for other browsers mentioned.

Pricing, plan by plan

Greasemonkey

Free
  • Open sourceFree
    • Unlimited scripts
    • Built-in editor
    • No account required

React Developer Tools

Free
  • FreeFree
    • Component tree
    • Props inspection
    • State tracking

Which should you pick?

Choose Greasemonkey if

  • You need userscript execution.
  • You want to start without paying.
  • You work on Firefox.
  • You also want built-in script editor.
Greasemonkey review

Choose React Developer Tools if

  • You need component inspection.
  • You want to start without paying.
  • You work on Chrome, Firefox, Edge.
  • You also want props/state viewing.
React Developer Tools review

Questions people ask

Is Greasemonkey or React Developer Tools better?
Neither clearly leads. Greasemonkey starts at Free and React Developer Tools at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Greasemonkey or React Developer Tools?
Greasemonkey starts at Free and React Developer Tools at Free.
Does Greasemonkey or React Developer Tools run on more platforms?
Greasemonkey runs on Firefox. React Developer Tools runs on Chrome, Firefox, Edge.
Can I use Greasemonkey for free?
Both have a free tier, so you can try either at no cost before committing.
What is Greasemonkey best used for?
Greasemonkey is most often used for restyling or de-cluttering a site you use daily, automating a repetitive action on a web application, adding a missing feature to a site you do not control, running userscripts on firefox for android. Of those, restyling or de-cluttering a site you use daily and automating a repetitive action on a web application are not what React Developer Tools is typically brought in for.
What can Greasemonkey do that React Developer Tools cannot?
Greasemonkey covers Userscript execution, Built-in script editor, GM. API, @resource support. React Developer Tools covers Component inspection, Props/State viewing, Performance profiler, Hooks debugging.

Answered from the vendors’ own pages

Greasemonkey: Is Greasemonkey still maintained?

Yes. Version 4.14 was released on 2 June 2026, and the project has an active repository, bug tracker and discussion groups.

Source
React Developer Tools: How much does React Developer Tools cost?

React Developer Tools is completely free. It is a free browser extension with no subscription fees or costs.

Source
Greasemonkey: Does Greasemonkey work on Chrome?

No. It is a Firefox extension and has never shipped for Chrome. Violentmonkey and Tampermonkey are the equivalents there.

Source
React Developer Tools: Is React Developer Tools available for download?

Yes. React Developer Tools is available as a free extension on the Chrome Web Store for download at no cost.

Source
Greasemonkey: Will Tampermonkey scripts run in Greasemonkey?

Often, but not always. Greasemonkey's API diverged from the conventions most shared scripts are written against, so a script may need its header or its GM calls adjusted.

Source
Greasemonkey: Does Greasemonkey run on mobile?

On Firefox for Android, from version 4.12. There is no iOS build, because Firefox on iOS cannot load extensions of this kind.

Source
Greasemonkey: What is the GM API?

The set of functions a userscript manager exposes to scripts, named after Greasemonkey, which defined it. Greasemonkey supports the promise-based GM. form including GM.xmlHttpRequest and GM.registerMenuCommand.

Source
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