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Cybersecurity · head to head

Cosign vs Ory Kratos

Cosign logo

Cosign

Cybersecurity

Signs and verifies container images and artifacts, with or without managing keys

From
Free
Rated
-
Full reviewWebsite
Ory Kratos logo

Ory Kratos

Cybersecurity

Headless identity and user management API

From
Free
Rated
-
Full reviewWebsite

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.; Ory Kratos headless means you build every screen, which is significant work compared with a hosted login page
  • They diverge on capability: Cosign covers Keyless signing, Ory Kratos covers Headless API.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Cosign and Ory Kratos actually diverge.

Attributes where Cosign and Ory Kratos differ
AttributeCosignOry Kratos
Pricing modelOpen source, no licence feeOpen-source self-hosted, with a paid managed network
PlatformsmacOS, Linux, Windows, DockerLinux, Docker, Kubernetes, Self-hosted

Identical on both: starting price (Free), free tier (Yes), user rating (Not yet rated), category (Cybersecurity).

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 Ory Kratos

  • Headless API
  • Self-service flows
  • Multi-factor authentication
  • Pluggable identity schemas

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 Ory Kratos
  • Attaching a signed bill of materials to a release so consumers can verify its provenancenot Ory Kratos
  • Meeting a customer or regulatory requirement for signed artifactsnot Ory Kratos
  • Verifying third-party images before they enter an internal registrynot Ory Kratos

Ory Kratos

  • Products needing complete control over the look and flow of authenticationnot Cosign
  • Applications that must not hand user identity data to a third partynot Cosign
  • Teams building identity as infrastructure across several servicesnot 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.

Ory Kratos

  • Headless means you build every screen, which is significant work compared with a hosted login page
  • More moving parts than a monolithic IAM: Kratos handles identity, and OAuth2 needs Ory Hydra alongside
  • Documentation assumes real familiarity with identity concepts and is not a gentle introduction
  • Self-hosting identity carries the security and availability burden that hosted providers absorb

Pricing, plan by plan

Cosign

Free
  • CosignFree
    • Apache-2.0
    • Public Sigstore infrastructure free to use
    • No usage limits published

Ory Kratos

Free
  • Self-hostedFree
    • Full identity server
    • All flows
    • Community support

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.
Cosign review

Choose Ory Kratos if

  • You need headless api.
  • You want to start without paying.
  • You work on Linux, Docker, Kubernetes, Self-hosted.
  • You also want self-service flows.
Ory Kratos review

Questions people ask

Is Cosign or Ory Kratos better?
Neither clearly leads. Cosign starts at Free and Ory Kratos at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Cosign or Ory Kratos?
Cosign starts at Free and Ory Kratos at Free.
Does Cosign or Ory Kratos run on more platforms?
Cosign runs on macOS, Linux, Windows, Docker. Ory Kratos runs on Linux, Docker, Kubernetes, Self-hosted.
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 Ory Kratos is typically brought in for.
What can Cosign do that Ory Kratos cannot?
Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations. Ory Kratos covers Headless API, Self-service flows, Multi-factor authentication, Pluggable identity schemas.

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.

Ory Kratos: Is Ory Kratos free?

Yes, open source and free to self-host. Ory Network is a paid managed service.

Cosign: Is signing alone enough?

No. Verification is a command somebody runs. Without an admission controller enforcing it, an unsigned image still runs.

Ory Kratos: What does headless mean here?

Kratos provides identity flows as APIs and no user interface. You build the login, registration and recovery screens yourself.

Cosign: 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.

Ory Kratos: Does Kratos do OAuth2?

No. Kratos handles user identity; OAuth2 and OpenID Connect provider functionality is Ory Hydra, a separate component.

Cosign: 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.

Cosign: 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.

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