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Developer Tools · head to head

Buildkite vs Cosign

Buildkite logo

Buildkite

Developer Tools

CI/CD pipelines that run on your own compute

From
Free
Free plan
Yes
Full reviewWebsite
Cosign logo

Cosign

Cybersecurity

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

From
Free
Free plan
Yes
Full reviewWebsite

The short version

  • Each has a real cost: Buildkite free plan caps at 5 users and 10 concurrent jobs, with 2,000 Linux vCPU minutes per month and 30 day build retention; 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.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Buildkite and Cosign actually diverge.

Attributes where Buildkite and Cosign differ
AttributeBuildkiteCosign
Pricing modelsubscriptionOpen source, no licence fee
PlatformsWebmacOS, Linux, Windows, Docker
CategoryDeveloper ToolsCybersecurity

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 Buildkite

Nothing recorded that Cosign does not also cover.

Only in Cosign

  • Keyless signing
  • Key and KMS signing
  • Registry-native storage
  • In-toto attestations
  • Offline verification
  • Trusted root and signing config

What people use each for

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

Buildkite

  • CI/CD pipeline automationnot Cosign
  • Test execution at scalenot Cosign
  • Deployment automationnot Cosign

Cosign

  • Signing container images in a build pipeline without managing long-lived private keysnot Buildkite
  • Attaching a signed bill of materials to a release so consumers can verify its provenancenot Buildkite
  • Meeting a customer or regulatory requirement for signed artifactsnot Buildkite
  • Verifying third-party images before they enter an internal registrynot Buildkite

Where each one falls short

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

Buildkite

  • Free plan caps at 5 users and 10 concurrent jobs, with 2,000 Linux vCPU minutes per month and 30 day build retention
  • Pro plan is $30 per active user per month, capped at 50 users, with only 10 of the up to 250 concurrent agents included before extra usage
  • Enterprise plan enforces a 30 user minimum even though pricing itself is custom
  • Hosted compute beyond included minutes is metered at $0.004 per vCPU minute on Linux and $0.02 per vCPU minute on Mac

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.

Pricing, plan by plan

Buildkite

Free
  • FreeFree
    • Up to 5 users
    • 10 concurrent jobs
    • 2000 Linux vCPU minutes monthly
  • Pro$30/month
    • Up to 50 users
    • 250 concurrent agents (10 included)
    • 4000 Linux vCPU minutes monthly
  • Enterprise$null/custom
    • Unlimited users (30 minimum)
    • Custom usage limits
    • Full platform access

Cosign

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

Which should you pick?

Choose Buildkite if

  • You want to start without paying.
Buildkite review

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

Questions people ask

Is Buildkite or Cosign better?
Neither clearly leads. Buildkite starts at Free and Cosign at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Buildkite or Cosign?
Buildkite starts at Free and Cosign at Free.
Does Buildkite or Cosign run on more platforms?
Buildkite runs on Web. Cosign runs on macOS, Linux, Windows, Docker.
Can I use Buildkite for free?
Both have a free tier, so you can try either at no cost before committing.
What is Buildkite best used for?
Buildkite is most often used for ci/cd pipeline automation, test execution at scale, deployment automation. Of those, ci/cd pipeline automation and test execution at scale are not what Cosign is typically brought in for.
What can Buildkite do that Cosign cannot?
Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations.

Answered from the vendors’ own pages

Buildkite: Can I use Buildkite without paying?

Yes, Buildkite offers a free plan that includes up to 5 users, 10 concurrent jobs, 2000 Linux vCPU minutes monthly, and 250k test executions per month at no cost.

Source
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.

Buildkite: What happens if I exceed my included compute minutes on Buildkite?

Hosted agent compute is charged separately at $0.004 per Linux vCPU minute and $0.02 per Mac vCPU minute, billed to the second with no minimums.

Source
Cosign: Is signing alone enough?

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

Buildkite: Do I need an annual commitment for Buildkite's Pro plan?

No, Buildkite's Pro plan is billed monthly at $30 per active user with no long-term contract required. All tiers include a 30-day all-access trial.

Source
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.

Buildkite: What user limits apply to each Buildkite plan?

Free plan supports up to 5 users, Pro plan supports up to 50 users, and Enterprise plan provides unlimited users with a 30-user minimum.

Source
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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