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Browser Extensions · head to head

FireMonkey vs JSON Viewer

FireMonkey logo

FireMonkey

Browser Extensions

User scripts and user styles in one Firefox extension

From
Free
Rated
-
Full reviewWebsite
JSON Viewer logo

JSON Viewer

Browser Extensions

View JSON documents in the browser

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.; JSON Viewer the project is MIT licensed open source code hosted on GitHub with no vendor and no paid tier
  • They diverge on capability: FireMonkey covers Scripts and styles together, JSON Viewer covers JSON formatting.
  • Prices and features above were last checked on 15 September 2026.

Where they differ

Only the attributes on which FireMonkey and JSON Viewer actually diverge.

Attributes where FireMonkey and JSON Viewer differ
AttributeFireMonkeyJSON Viewer
Pricing modelopen-sourcefree
PlatformsFirefoxChrome, Firefox, Edge
FoundedUnknown2015

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 JSON Viewer

  • JSON formatting
  • Syntax highlighting
  • Tree view
  • Search functionality
  • Chrome support
  • Firefox support
  • Edge 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 JSON Viewer
  • Restyling sites with CSS alongside scripted behaviour changesnot JSON Viewer
  • Editing scripts in a full editor inside the browsernot JSON Viewer
  • Injecting CSS globally across every sitenot JSON Viewer
  • Managing a mixed library of scripts and styles from one dashboardnot JSON Viewer

JSON Viewer

No use cases recorded yet. See the JSON Viewer review.

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.

JSON Viewer

  • The project is MIT licensed open source code hosted on GitHub with no vendor and no paid tier

Pricing, plan by plan

FireMonkey

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

JSON Viewer

Free
  • FreeFree
    • Syntax highlighting
    • Collapsible tree
    • Search

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 JSON Viewer if

  • You need json formatting.
  • You want to start without paying.
  • You work on Chrome, Firefox, Edge.
  • You also want syntax highlighting.
JSON Viewer review

Questions people ask

Is FireMonkey or JSON Viewer better?
Neither clearly leads. FireMonkey starts at Free and JSON Viewer at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, FireMonkey or JSON Viewer?
FireMonkey starts at Free and JSON Viewer at Free.
Does FireMonkey or JSON Viewer run on more platforms?
FireMonkey runs on Firefox. JSON Viewer runs on Chrome, Firefox, Edge.
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 JSON Viewer is typically brought in for.
What can FireMonkey do that JSON Viewer cannot?
FireMonkey covers Scripts and styles together, Monaco editor with ESLint, Unlimited client-side storage, Global injection. JSON Viewer covers JSON formatting, Syntax highlighting, Tree view, Search functionality.

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
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
FireMonkey: Is FireMonkey open source?

Yes, under the MPL-2.0 licence.

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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