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Browser Extensions · head to head

Greasemonkey vs Keeper

Greasemonkey logo

Greasemonkey

Browser Extensions

The original userscript manager, for Firefox

From
Free
Rated
-
Full reviewWebsite
Keeper logo

Keeper

Browser Extensions

Protect your passwords and private information

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.; Keeper free tier is severely limited to 10 passwords on a single device; essentially a trial rather than a usable free version
  • They diverge on capability: Greasemonkey covers Userscript execution, Keeper covers Password management.
  • Prices and features above were last checked on 15 September 2026.

Where they differ

Only the attributes on which Greasemonkey and Keeper actually diverge.

Attributes where Greasemonkey and Keeper differ
AttributeGreasemonkeyKeeper
Pricing modelopen-sourceUnknown
PlatformsFirefoxChrome, Firefox, Edge, Safari, Brave, Opera, iOS, Android, macOS, Windows
FoundedUnknown2011

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 Keeper

  • Password management
  • Zero-knowledge encryption
  • Secure file storage
  • BreachWatch
  • Chrome support
  • Firefox support
  • Edge support
  • Safari 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 Keeper
  • Automating a repetitive action on a web applicationnot Keeper
  • Adding a missing feature to a site you do not controlnot Keeper
  • Running userscripts on Firefox for Androidnot Keeper
  • Writing and testing your own scripts in the browsernot Keeper

Keeper

  • Business and enterprise password management with zero-knowledge encryptionnot Greasemonkey
  • Privileged access management for admin and service accountsnot Greasemonkey
  • Secure remote access and privileged session recordingnot Greasemonkey
  • Application secrets management through Secrets Managernot Greasemonkey
  • Government deployments requiring FedRAMP Highnot 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.

Keeper

  • Free tier is severely limited to 10 passwords on a single device; essentially a trial rather than a usable free version
  • Personal plan at $1.79/month is promotional pricing; regular price is higher, making budget comparison difficult

Pricing, plan by plan

Greasemonkey

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

Keeper

Free
  • FreeFree
    • 10 passwords max
    • Single device only
    • No sync
  • Personal$1.79/month
    • Unlimited passwords
    • All devices
    • 2FA support
  • Family$3.83/month
    • Up to 5 users
    • Unlimited storage
    • Shared vaults

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 Keeper if

  • You need password management.
  • You want to start without paying.
  • You work on Chrome, Firefox, Edge, Safari, Brave, Opera, iOS, Android, macOS, Windows.
  • You also want zero-knowledge encryption.
Keeper review

Questions people ask

Is Greasemonkey or Keeper better?
Neither clearly leads. Greasemonkey starts at Free and Keeper at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Greasemonkey or Keeper?
Greasemonkey starts at Free and Keeper at Free.
Does Greasemonkey or Keeper run on more platforms?
Greasemonkey runs on Firefox. Keeper runs on Chrome, Firefox, Edge, Safari, Brave, Opera, iOS, Android, macOS, Windows.
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 Keeper is typically brought in for.
What can Greasemonkey do that Keeper cannot?
Greasemonkey covers Userscript execution, Built-in script editor, GM. API, @resource support. Keeper covers Password management, Zero-knowledge encryption, Secure file storage, BreachWatch.

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
Keeper: Is there a free version of Keeper?

Keeper offers a free version with very limited functionality: it stores only 10 passwords on a single mobile device with no cross-device sync. A 30-day free trial provides full access to all features.

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
Keeper: What are Keeper's paid pricing plans?

Keeper Personal starts at $1.79/month (promotional pricing) with annual billing. Keeper Family covers up to 5 users at $3.83/month annually. Both include unlimited password storage, cross-device sync, and 2FA support.

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
Keeper: What browsers and devices does Keeper support?

Keeper has browser extensions for Chrome, Firefox, Edge, Safari, Brave, and Opera. It also offers native apps for iOS, Android, macOS, Windows, and web access.

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
Keeper: Does Keeper support 2FA and passkeys?

Yes, Keeper stores and autofills FIDO2 passkeys and supports multiple 2FA methods including TOTP, SMS, and WebAuthn. Biometric login (fingerprint/face recognition) is also supported.

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
Keeper: How secure is Keeper?

Keeper uses zero-knowledge architecture where data is encrypted and decrypted only on your device. Only you can access your vault, and the company cannot see your passwords or data.

Source
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