Softwr

Browser Extensions · head to head

FireMonkey vs Keeper

FireMonkey logo

FireMonkey

Browser Extensions

User scripts and user styles in one Firefox extension

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: FireMonkey firefox only, and requires a recent one: version 93 on desktop, 113 on Android.; 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: FireMonkey covers Scripts and styles together, Keeper covers Password management.
  • Prices and features above were last checked on 15 September 2026.

Where they differ

Only the attributes on which FireMonkey and Keeper actually diverge.

Attributes where FireMonkey and Keeper differ
AttributeFireMonkeyKeeper
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 FireMonkey

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

FireMonkey

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

Keeper

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

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

FireMonkey

Free
  • Open sourceFree
    • MPL-2.0 licensed
    • Unlimited scripts and styles
    • 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 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 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 FireMonkey or Keeper better?
Neither clearly leads. FireMonkey 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, FireMonkey or Keeper?
FireMonkey starts at Free and Keeper at Free.
Does FireMonkey or Keeper run on more platforms?
FireMonkey runs on Firefox. Keeper runs on Chrome, Firefox, Edge, Safari, Brave, Opera, iOS, Android, macOS, Windows.
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 Keeper is typically brought in for.
What can FireMonkey do that Keeper cannot?
FireMonkey covers Scripts and styles together, Monaco editor with ESLint, Unlimited client-side storage, Global injection. Keeper covers Password management, Zero-knowledge encryption, Secure file storage, BreachWatch.

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
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
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
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
FireMonkey: Is FireMonkey open source?

Yes, under the MPL-2.0 licence.

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
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
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
FireMonkey: What editor does FireMonkey use?

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

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
Share

Related pages

More on FireMonkey

More on Keeper

Keep looking

Other head to heads