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Cybersecurity · head to head

Cosign vs Syft

Cosign logo

Cosign

Cybersecurity

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

From
Free
Rated
-
Full reviewWebsite
Syft logo

Syft

Cybersecurity

Generates a software bill of materials from images, filesystems and archives

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.; Syft lockfile parsing can drop packages silently. An open issue filed in August 2026 reports the yarn v1 cataloguer returning 118 of 745 packages with no error raised, which means a complete bill of materials and an 84 percent incomplete one look identical to the caller.
  • They diverge on capability: Cosign covers Keyless signing, Syft covers Multi-format output.
  • Prices and features above were last checked on 31 August 2026.

Where they differ

Only the attributes on which Cosign and Syft actually diverge.

Attributes where Cosign and Syft differ
AttributeCosignSyft

Identical on both: starting price (Free), pricing model (Open source, no licence fee), free tier (Yes), platforms (macOS, Linux, Windows, Docker), 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
  • Offline verification
  • Trusted root and signing config

Only in Syft

  • Multi-format output
  • Broad ecosystem coverage
  • Binary classifiers
  • Library and CLI
  • Pairs with Grype

Both cover

  • In-toto attestations

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

Syft

  • Producing a bill of materials for a customer or regulator that requires onenot Cosign
  • Feeding an inventory into a vulnerability scanner rather than scanning images directlynot Cosign
  • Recording what shipped in a build so a future disclosure can be answered quicklynot Cosign
  • Public sector work where an SBOM is a contractual deliverablenot 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.

Syft

  • Lockfile parsing can drop packages silently. An open issue filed in August 2026 reports the yarn v1 cataloguer returning 118 of 745 packages with no error raised, which means a complete bill of materials and an 84 percent incomplete one look identical to the caller.
  • Fidelity varies sharply by ecosystem. Conan for C and C++, Haskell and Terraform get cataloguer support with no licence data, no dependency relationships and no file ownership, so a C and C++ shop gets the least from it.
  • Binary classification yields no licence or dependency metadata, and vendored or statically linked code is exactly where supply chain risk hides, so the blind spot and the risk overlap.
  • Incorrect CPE values and CPE collisions are recorded as open issues, and since Grype matches on CPE and PURL, an inventory error becomes a false negative in the security report downstream.
  • An inventory is not a risk assessment. Even a perfect bill of materials says a vulnerable version is present, never that the vulnerable function is called, and the triage burden lands entirely on the reader.

Pricing, plan by plan

Cosign

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

Syft

Free
  • SyftFree
    • Apache-2.0
    • No usage limits
    • Community support
  • Anchore Enterprise$undefined/year
    • Policy enforcement and reporting
    • Federal and commercial tiers
    • Pricing not published, quoted on request

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 Syft if

  • You need multi-format output.
  • You want to start without paying.
  • You work on macOS, Linux, Windows, Docker.
  • You also want broad ecosystem coverage.
Syft review

Questions people ask

Is Cosign or Syft better?
Neither clearly leads. Cosign starts at Free and Syft at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Cosign or Syft?
Cosign starts at Free and Syft at Free.
Does Cosign or Syft run on more platforms?
Both run on macOS, Linux, Windows, Docker, so platform support will not decide this one for you.
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 Syft is typically brought in for.
What can Cosign do that Syft cannot?
Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, Offline verification. Syft covers Multi-format output, Broad ecosystem coverage, Binary classifiers, Library and CLI. Both handle In-toto attestations.

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.

Syft: Does Syft find vulnerabilities?

No. It produces an inventory. Grype, from the same company, matches that inventory against vulnerability feeds. They are separate tools and the distinction is frequently lost.

Cosign: Is signing alone enough?

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

Syft: Does anything in the Anchore stack do reachability analysis?

No. Neither Syft, Grype nor the commercial Anchore platform performs call graph or reachability analysis, so none of them tells you whether a vulnerable code path is actually invoked.

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.

Syft: Is it a CNCF or OpenSSF project?

No. It is single-vendor open source owned by Anchore, with no foundation governance. That is a different licence risk profile from Sigstore.

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.

Syft: What does Anchore Enterprise cost?

Not published. The pricing page is contact-sales only, with named but unpriced commercial and federal tiers.

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.

Syft: How do I know my SBOM is complete?

You largely cannot, which is the honest answer. Silent partial parsing is a known open defect, so a bill of materials used for compliance should be spot-checked against a known dependency list.

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