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Browser Extensions · head to head

Greasemonkey vs SimilarWeb

Greasemonkey logo

Greasemonkey

Browser Extensions

The original userscript manager, for Firefox

From
Free
Rated
-
Full reviewWebsite
SimilarWeb logo

SimilarWeb

Browser Extensions

Website traffic and competitive analysis

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.; SimilarWeb browser extension data accuracy is lower than full platform
  • They diverge on capability: Greasemonkey covers Userscript execution, SimilarWeb covers Traffic analytics.
  • Prices and features above were last checked on 15 September 2026.

Where they differ

Only the attributes on which Greasemonkey and SimilarWeb actually diverge.

Attributes where Greasemonkey and SimilarWeb differ
AttributeGreasemonkeySimilarWeb
Pricing modelopen-sourcefreemium
PlatformsFirefoxWeb, Browser Extension
FoundedUnknown2007

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 SimilarWeb

  • Traffic analytics
  • Audience insights
  • Competitor research
  • Industry analysis
  • 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 SimilarWeb
  • Automating a repetitive action on a web applicationnot SimilarWeb
  • Adding a missing feature to a site you do not controlnot SimilarWeb
  • Running userscripts on Firefox for Androidnot SimilarWeb
  • Writing and testing your own scripts in the browsernot SimilarWeb

SimilarWeb

  • Analyzing competitor advertising across display, search, socialnot Greasemonkey
  • Understanding traffic loss to search and AI recommendationsnot Greasemonkey
  • Tracking brand visibility across ChatGPT and AI chatbotsnot Greasemonkey
  • Optimizing Amazon product placement with marketplace analyticsnot Greasemonkey
  • Identifying high-intent prospects at optimal buying momentsnot 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.

SimilarWeb

  • Browser extension data accuracy is lower than full platform
  • Full platform pricing is not transparent and requires quote-based inquiry

Pricing, plan by plan

Greasemonkey

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

SimilarWeb

Free
  • FreeFree
    • Traffic overview
    • Engagement metrics
    • Similar sites

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 SimilarWeb if

  • You need traffic analytics.
  • You want to start without paying.
  • You work on Web, Browser Extension.
  • You also want audience insights.
SimilarWeb review

Questions people ask

Is Greasemonkey or SimilarWeb better?
Neither clearly leads. Greasemonkey starts at Free and SimilarWeb at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Greasemonkey or SimilarWeb?
Greasemonkey starts at Free and SimilarWeb at Free.
Does Greasemonkey or SimilarWeb run on more platforms?
Greasemonkey runs on Firefox. SimilarWeb runs on Web, Browser Extension.
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 SimilarWeb is typically brought in for.
What can Greasemonkey do that SimilarWeb cannot?
Greasemonkey covers Userscript execution, Built-in script editor, GM. API, @resource support. SimilarWeb covers Traffic analytics, Audience insights, Competitor research, Industry analysis.

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
SimilarWeb: How much does Similarweb cost?

Similarweb does not publish pricing. Custom packages are available for businesses and enterprises. Self-service options are available for entrepreneurs and small teams. Customers must start a free trial or contact sales to receive a quote.

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
SimilarWeb: Does Similarweb offer a free trial?

Yes. Similarweb offers free trials for its various products. Users can start a free trial through their registration page or contact support to switch between different product trials.

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
SimilarWeb: What products does Similarweb offer?

Similarweb offers the Competitive Intelligence Suite, Strategic SEO Suite, Ads Intelligence Suite, Gen AI Intelligence Suite, AI Studio with natural language queries, custom data feeds, API access, and managed services with custom dashboards.

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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