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Browser Extensions · head to head

FireMonkey vs Stylus

FireMonkey logo

FireMonkey

Browser Extensions

User scripts and user styles in one Firefox extension

From
Free
Rated
-
Full reviewWebsite
Stylus logo

Stylus

Browser Extensions

Restyle the web with custom CSS

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.; Stylus crashes and instability when applying certain styles
  • They diverge on capability: FireMonkey covers Scripts and styles together, Stylus covers Custom CSS injection.
  • Prices and features above were last checked on 15 September 2026.

Where they differ

Only the attributes on which FireMonkey and Stylus actually diverge.

Attributes where FireMonkey and Stylus differ
AttributeFireMonkeyStylus
Pricing modelopen-sourcefree
PlatformsFirefoxChrome, Firefox, Edge, Opera
FoundedUnknown2017

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 FireMonkey

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

Only in Stylus

  • Custom CSS injection
  • Style management
  • userstyles.world integration
  • Built-in editor
  • Chrome support
  • Firefox support
  • Edge support
  • Opera support

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 Stylus
  • Restyling sites with CSS alongside scripted behaviour changesnot Stylus
  • Editing scripts in a full editor inside the browsernot Stylus
  • Injecting CSS globally across every sitenot Stylus
  • Managing a mixed library of scripts and styles from one dashboardnot Stylus

Stylus

  • Customizing website appearance with community-created CSS themesnot FireMonkey
  • Writing personal style overrides for specific websitesnot FireMonkey
  • Managing multiple styles across different websites automaticallynot FireMonkey
  • Searching and installing user-styles for current websitesnot FireMonkey
  • Migrating style collections from Stylish extensionnot 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.

Stylus

  • Crashes and instability when applying certain styles
  • No visual element selector tool for identifying page elements to style
  • Security risk if downloading and applying untrusted user-created styles

Pricing, plan by plan

FireMonkey

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

Stylus

Free
  • FreeFree
    • Custom CSS
    • Style library
    • Style editor

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 Stylus if

  • You need custom css injection.
  • You want to start without paying.
  • You work on Chrome, Firefox, Edge, Opera.
  • You also want style management.
Stylus review

Questions people ask

Is FireMonkey or Stylus better?
Neither clearly leads. FireMonkey starts at Free and Stylus at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, FireMonkey or Stylus?
FireMonkey starts at Free and Stylus at Free.
Does FireMonkey or Stylus run on more platforms?
FireMonkey runs on Firefox. Stylus runs on Chrome, Firefox, Edge, Opera.
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 Stylus is typically brought in for.
What can FireMonkey do that Stylus cannot?
FireMonkey covers Scripts and styles together, Monaco editor with ESLint, Unlimited client-side storage, Global injection. Stylus covers Custom CSS injection, Style management, userstyles.world integration, Built-in editor.

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
Stylus: Is Stylus free?

Yes. Stylus is completely free and open-source, available for Chrome, Firefox, Edge, and Opera browsers.

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
Stylus: Can I use Stylus to change the browser UI?

No. Due to WebExtensions security restrictions, Stylus can only customize website pages, not the browser interface itself.

Source
FireMonkey: Is FireMonkey open source?

Yes, under the MPL-2.0 licence.

Source
Stylus: What CSS pre-processors does Stylus support?

Stylus supports CSS, LESS, and Stylus syntax with built-in linting using Stylelint and CSSLint-mod with customizable rules.

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
FireMonkey: What editor does FireMonkey use?

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

Source
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