Cybersecurity · head to head
Cosign vs Userscripts
Cosign
Cybersecurity
Signs and verifies container images and artifacts, with or without managing keys
- From
- Free
- Rated
- -
Userscripts
Browser Extensions
Open-source userscript manager for Safari on Mac and iOS
- From
- Free
- Rated
- -
The short version
- Each has a real cost: Cosign keyless signing inherits every weakness of the identity provider behind it. Sigstore’s own threat model states that if an identity provider is compromised, Sigstore will issue certificates to those identities, so a compromised account produces perfectly valid signatures.; Userscripts safari cannot let extensions bypass a site's Content Security Policy, so strict sites produce "Refused to execute a script" errors that the @inject-into workaround does not always fix.
- They diverge on capability: Cosign covers Keyless signing, Userscripts covers Built-in script editor.
- Prices and features above were last checked on 17 September 2026.
Where they differ
Only the attributes on which Cosign and Userscripts actually diverge.
| Attribute | Cosign | Userscripts |
|---|---|---|
| Pricing model | Open source, no licence fee | open-source |
| Platforms | macOS, Linux, Windows, Docker | Safari, macOS, iOS |
| Category | Cybersecurity | Browser Extensions |
Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated).
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 Cosign
- Keyless signing
- Key and KMS signing
- Registry-native storage
- In-toto attestations
- Offline verification
- Trusted root and signing config
Only in Userscripts
- Built-in script editor
- Standard metadata support
- GM API
- Remote script updating
- iCloud sync
- Per-page popup
What people use each for
The jobs each tool is most often brought in to do.
Cosign
- Signing container images in a build pipeline without managing long-lived private keysnot Userscripts
- Attaching a signed bill of materials to a release so consumers can verify its provenancenot Userscripts
- Meeting a customer or regulatory requirement for signed artifactsnot Userscripts
- Verifying third-party images before they enter an internal registrynot Userscripts
Userscripts
- Running userscripts on Safari without paying for Tampermonkeynot Cosign
- Running userscripts on an iPhone or iPadnot Cosign
- Writing scripts on a Mac and syncing them to iOSnot Cosign
- Blocking or restyling site elements Safari content blockers cannot reachnot Cosign
- Keeping a script library under an open-source licencenot Cosign
Where each one falls short
Documented limitations, not opinions. Every one is a constraint you would hit in normal use.
Cosign
- Keyless signing inherits every weakness of the identity provider behind it. Sigstore’s own threat model states that if an identity provider is compromised, Sigstore will issue certificates to those identities, so a compromised account produces perfectly valid signatures.
- A signature proves who signed, never whether they should have. The documentation is explicit that Sigstore cannot determine authorisation, so every consumer must write and maintain their own identity and issuer policy or verification means nothing.
- Nothing is enforced without an admission controller. Signing changes what you can prove, not what runs, and the official policy controller has a small maintainer base for a component sitting in a cluster admission path.
- Upgrades break pipelines. Version 3 changed defaults, version 4 is announced as removing legacy functionality and roughly half the command line flags, and two official client libraries still lacked support for the new log format as of mid 2026.
- Signatures do not expire. An artifact signed before a maintainer account was compromised and one signed after are indistinguishable unless somebody is actively monitoring the transparency log, and almost nobody is.
Userscripts
- Safari cannot let extensions bypass a site's Content Security Policy, so strict sites produce "Refused to execute a script" errors that the @inject-into workaround does not always fix.
- Apple only. There is no Chrome, Firefox or Edge build, so it cannot be a cross-browser answer.
- iCloud sync is documented as having delays, which is awkward when editing the same script on two devices.
- Requires macOS 12 and Safari 14.1, or iOS 15.1, so older Apple hardware is excluded.
- GPL v3 means a commercial licence is required for non-open-source use, which matters if you are embedding rather than just using it.
Pricing, plan by plan
Cosign
Free- CosignFree
- Apache-2.0
- Public Sigstore infrastructure free to use
- No usage limits published
Userscripts
Free- FreeFree
- Full functionality
- GPL v3 licensed
- macOS, iOS and iPadOS
Which should you pick?
Choose Cosign if
- You need keyless signing.
- You want to start without paying.
- You work on macOS, Linux, Windows, Docker.
- You also want key and kms signing.
Choose Userscripts if
- You need built-in script editor.
- You want to start without paying.
- You work on Safari, macOS, iOS.
- You also want standard metadata support.
Questions people ask
- Is Cosign or Userscripts better?
- Neither clearly leads. Cosign starts at Free and Userscripts at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Cosign or Userscripts?
- Cosign starts at Free and Userscripts at Free.
- Does Cosign or Userscripts run on more platforms?
- Cosign runs on macOS, Linux, Windows, Docker. Userscripts runs on Safari, macOS, iOS.
- Can I use Cosign for free?
- Both have a free tier, so you can try either at no cost before committing.
- What is Cosign best used for?
- Cosign is most often used for signing container images in a build pipeline without managing long-lived private keys, attaching a signed bill of materials to a release so consumers can verify its provenance, meeting a customer or regulatory requirement for signed artifacts, verifying third-party images before they enter an internal registry. Of those, signing container images in a build pipeline without managing long-lived private keys and attaching a signed bill of materials to a release so consumers can verify its provenance are not what Userscripts is typically brought in for.
- What can Cosign do that Userscripts cannot?
- Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations. Userscripts covers Built-in script editor, Standard metadata support, GM API, Remote script updating.
Answered from the vendors’ own pages
Cosign: Does Cosign tell me if an image is vulnerable?
No. It has no vulnerability knowledge whatsoever. It can carry an SBOM as a signed attestation but never reads it. Pair it with a scanner.
Userscripts: Is Userscripts for Safari free?
Yes, free on the App Store and licensed under GPL v3. A commercial licence is required for use in something that is not itself open source.
SourceCosign: Is signing alone enough?
No. Verification is a command somebody runs. Without an admission controller enforcing it, an unsigned image still runs.
Userscripts: Does it work on iPhone?
Yes, on iOS and iPadOS 15.1 or later, which makes it one of the few ways to run userscripts on an iPhone.
SourceCosign: What does a bare cosign verify actually prove?
Very little. Without a pinned certificate identity and OIDC issuer, it accepts a valid signature from any identity at all.
Userscripts: Why do I get "Refused to execute a script" errors?
Safari does not let extensions bypass a site's Content Security Policy the way other browsers do. The documented workaround is changing the script's @inject-into setting, though it does not resolve every case.
SourceCosign: What is the risk of keyless signing?
Your OIDC provider becomes the root of trust. Compromise of that account yields genuine, verifiable signatures, so account security is the control that matters.
Userscripts: Do my scripts sync between Mac and iPhone?
Yes, over iCloud, though the project notes the sync can be delayed rather than immediate.
SourceCosign: Should we expect breaking changes?
Yes. Version 4 is announced to remove roughly half the flags, and a post-quantum migration is named as a further breaking change after that.
Userscripts: What are the system requirements?
macOS 12 or later with Safari 14.1 or later, or iOS and iPadOS 15.1 or later.
SourceRelated pages
More on Userscripts
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