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Browser Extensions · head to head

FireMonkey vs Greasemonkey

FireMonkey logo

FireMonkey

Browser Extensions

User scripts and user styles in one Firefox extension

From
Free
Rated
-
Full reviewWebsite
Greasemonkey logo

Greasemonkey

Browser Extensions

The original userscript manager, for Firefox

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: FireMonkey firefox only, and requires a recent one: version 93 on desktop, 113 on Android.; Greasemonkey firefox only. There is no Chrome, Edge or Safari build and there never has been.
  • They diverge on capability: FireMonkey covers Scripts and styles together, Greasemonkey covers Userscript execution.
  • Prices and features above were last checked on 15 September 2026.

Where they differ

Only the attributes on which FireMonkey and Greasemonkey actually diverge.

Attributes where FireMonkey and Greasemonkey differ
AttributeFireMonkeyGreasemonkey

Identical on both: starting price (Free), pricing model (open-source), free tier (Yes), platforms (Firefox), 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 FireMonkey

  • Scripts and styles together
  • Monaco editor with ESLint
  • Unlimited client-side storage
  • Global injection
  • Notifications and clipboard

Only in Greasemonkey

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

Both cover

  • Firefox for Android

What people use each for

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

FireMonkey

  • Running user scripts and user styles without two separate extensionsnot Greasemonkey
  • Restyling sites with CSS alongside scripted behaviour changesnot Greasemonkey
  • Editing scripts in a full editor inside the browsernot Greasemonkey
  • Injecting CSS globally across every sitenot Greasemonkey
  • Managing a mixed library of scripts and styles from one dashboardnot Greasemonkey

Greasemonkey

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

Where each one falls short

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

FireMonkey

  • Firefox only, and requires a recent one: version 93 on desktop, 113 on Android.
  • Not a drop-in replacement for Greasemonkey, Tampermonkey or Stylus. The project says so itself, so an existing library may need adjusting.
  • A much smaller user base than Tampermonkey or Violentmonkey, which means fewer people have hit the bug you are about to hit.
  • No Chrome, Edge or Safari build, so it cannot be the answer for anyone working across browsers.
  • Combining scripts and styles in one extension also combines the blast radius: one extension with permission to inject both into every page.

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.

Pricing, plan by plan

FireMonkey

Free
  • Open sourceFree
    • MPL-2.0 licensed
    • Unlimited scripts and styles
    • No account required

Greasemonkey

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

Which should you pick?

Choose FireMonkey if

  • You need scripts and styles together.
  • You want to start without paying.
  • You work on Firefox.
  • You also want monaco editor with eslint.
FireMonkey review

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

Questions people ask

Is FireMonkey or Greasemonkey better?
Neither clearly leads. FireMonkey starts at Free and Greasemonkey at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, FireMonkey or Greasemonkey?
FireMonkey starts at Free and Greasemonkey at Free.
Does FireMonkey or Greasemonkey run on more platforms?
Both run on Firefox, so platform support will not decide this one for you.
Can I use FireMonkey for free?
Both have a free tier, so you can try either at no cost before committing.
What is FireMonkey best used for?
FireMonkey is most often used for running user scripts and user styles without two separate extensions, restyling sites with css alongside scripted behaviour changes, editing scripts in a full editor inside the browser, injecting css globally across every site. Of those, running user scripts and user styles without two separate extensions and restyling sites with css alongside scripted behaviour changes are not what Greasemonkey is typically brought in for.
What can FireMonkey do that Greasemonkey cannot?
FireMonkey covers Scripts and styles together, Monaco editor with ESLint, Unlimited client-side storage, Global injection. Greasemonkey covers Userscript execution, Built-in script editor, GM. API, @resource support. Both handle Firefox for Android.

Answered from the vendors’ own pages

FireMonkey: What makes FireMonkey different from Violentmonkey?

It manages user styles as well as user scripts. The usual arrangement is a script manager plus a separate style manager such as Stylus; FireMonkey replaces both with one extension.

Source
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
FireMonkey: Which browsers does FireMonkey support?

Firefox only. Desktop requires Firefox 93 or later and Android requires 113, with an API minimum of 102.

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
FireMonkey: Is FireMonkey open source?

Yes, under the MPL-2.0 licence.

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
FireMonkey: Will my existing Tampermonkey scripts work?

Not necessarily. The project states that while it shares functionality with Greasemonkey, Tampermonkey and Stylus, there are differences, so scripts and styles written for those may need adjusting.

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
FireMonkey: What editor does FireMonkey use?

Current versions use the Monaco editor with ESLint, the same editor component that powers VS Code.

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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