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Cybersecurity · head to head

Ory Kratos vs Sigstore

Ory Kratos logo

Ory Kratos

Cybersecurity

Headless identity and user management API

From
Free
Rated
-
Full reviewWebsite
Sigstore logo

Sigstore

Cybersecurity

Free public signing and transparency infrastructure for open source artifacts

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: Ory Kratos headless means you build every screen, which is significant work compared with a hosted login page; Sigstore the security model depends on somebody watching the log. The documentation states that compromise of an identity provider or of Fulcio itself is detectable only if third parties monitor the transparency log, the monitoring tool is a community-tier rather than core project, and almost no consumer runs one.
  • They diverge on capability: Ory Kratos covers Headless API, Sigstore covers Fulcio.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

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

Attributes where Ory Kratos and Sigstore differ
AttributeOry KratosSigstore
Pricing modelOpen-source self-hosted, with a paid managed networkOpen source, public instance free to use
PlatformsLinux, Docker, Kubernetes, Self-hostedWeb, Linux, macOS, Windows, 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 Ory Kratos

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

Only in Sigstore

  • Fulcio
  • Rekor
  • Keyless signing
  • Multi-language clients
  • Timestamp authority
  • Neutral governance

What people use each for

The jobs each tool is most often brought in to do.

Ory Kratos

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

Sigstore

  • Open source projects signing releases without running a certificate authoritynot Ory Kratos
  • Organisations meeting a signed-artifact requirement without buying a signing productnot Ory Kratos
  • Publishing provenance that a consumer can verify independently of younot Ory Kratos
  • Self-hosting the same components where a public log is unacceptablenot Ory Kratos

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

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

Sigstore

  • The security model depends on somebody watching the log. The documentation states that compromise of an identity provider or of Fulcio itself is detectable only if third parties monitor the transparency log, the monitoring tool is a community-tier rather than core project, and almost no consumer runs one.
  • It is a 99.5 percent objective with no service level agreement, which permits several hours of downtime a month and offers no remedy. A pipeline that signs on every build has taken a hard dependency on a free service with no contract behind it.
  • Log scale is a live engineering problem rather than a theoretical one. The active shard holds billions of entries, the log has already been sharded twice, and sharding version 1 requires stopping traffic, which is why a replacement was built.
  • Ten-minute certificates make trust depend on log availability. Verifying an older signature relies on the log entry proving it was made inside that window, so a lost or unreachable entry can render a valid artifact unverifiable.
  • Migration debt is substantial and ongoing. Version 2 of the log is generally available but not the public default, the signing client has an announced breaking release ahead, some official clients lag the new log format, and a post-quantum migration is named as the next break after that.

Pricing, plan by plan

Ory Kratos

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

Sigstore

Free
  • Public good instanceFree
    • Free to everyone with no contract
    • 99.5 percent availability objective, not an agreement
    • 100KB cap per attestation upload
  • Self-hostedFree
    • Apache-2.0
    • Run your own Fulcio and Rekor
    • Rekor v2 available for self-hosters

Which should you pick?

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

Choose Sigstore if

  • You need fulcio.
  • You want to start without paying.
  • You work on Web, Linux, macOS, Windows, Self-hosted.
  • You also want rekor.
Sigstore review

Questions people ask

Is Ory Kratos or Sigstore better?
Neither clearly leads. Ory Kratos starts at Free and Sigstore at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Ory Kratos or Sigstore?
Ory Kratos starts at Free and Sigstore at Free.
Does Ory Kratos or Sigstore run on more platforms?
Ory Kratos runs on Linux, Docker, Kubernetes, Self-hosted. Sigstore runs on Web, Linux, macOS, Windows, Self-hosted.
Can I use Ory Kratos for free?
Both have a free tier, so you can try either at no cost before committing.
What is Ory Kratos best used for?
Ory Kratos is most often used for products needing complete control over the look and flow of authentication, applications that must not hand user identity data to a third party, teams building identity as infrastructure across several services. Of those, products needing complete control over the look and flow of authentication and applications that must not hand user identity data to a third party are not what Sigstore is typically brought in for.
What can Ory Kratos do that Sigstore cannot?
Ory Kratos covers Headless API, Self-service flows, Multi-factor authentication, Pluggable identity schemas. Sigstore covers Fulcio, Rekor, Keyless signing, Multi-language clients.

Answered from the vendors’ own pages

Ory Kratos: Is Ory Kratos free?

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

Sigstore: Is the public instance really free?

Yes, with no contract and no paid tier. That is also the weakness: a 99.5 percent objective with no agreement, no remedy and support through Slack.

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.

Sigstore: Has the public log moved to Rekor v2?

No. Version 2 reached general availability in October 2025 and self-hosters can use it, but the public instance still defaults to version 1 and the project has said it will for the foreseeable future.

Ory Kratos: Does Kratos do OAuth2?

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

Sigstore: Does Sigstore make my dependencies safe?

No, and this is a category error worth avoiding. It tells you who published something. It has no knowledge of what the artifact contains or whether it is vulnerable.

Sigstore: What are the rate limits?

Not published. Only the 100KB cap per attestation upload is documented, so do not design a high-volume pipeline around assumed throughput.

Sigstore: Should we self-host it?

If a public record of every signature is unacceptable, or if a free service with no agreement cannot sit in your build path, then yes. Otherwise the public instance is what most projects use.

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