Cybersecurity · head to head
Cosign vs Spacelift
Cosign
Cybersecurity
Signs and verifies container images and artifacts, with or without managing keys
- From
- Free
- Free plan
- Yes
Spacelift
Developer Tools
Infrastructure-as-code orchestration for Terraform, OpenTofu, Pulumi and Kubernetes
- From
- Free
- Free plan
- Yes
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.; Spacelift users are unlimited and private workers are metered, so deployment concurrency rather than headcount drives the bill, which inverts how most engineering budgets are built and is easy to under-forecast.
- They diverge on capability: Cosign covers Keyless signing, Spacelift covers Multi-tool orchestration.
- Prices and features above were last checked on 31 August 2026.
Where they differ
Only the attributes on which Cosign and Spacelift actually diverge.
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 Spacelift
- Multi-tool orchestration
- Policy as code
- Private workers
- Spaces
- Blueprints
- Drift detection
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 Spacelift
- Attaching a signed bill of materials to a release so consumers can verify its provenancenot Spacelift
- Meeting a customer or regulatory requirement for signed artifactsnot Spacelift
- Verifying third-party images before they enter an internal registrynot Spacelift
Spacelift
- Platform teams running infrastructure changes through approval gates rather than through application CInot Cosign
- Organisations standardising Terraform and OpenTofu across many teams with policy enforcementnot Cosign
- Estates needing private runners so cloud credentials never leave the networknot Cosign
- Teams wanting drift detection and reconciliation rather than plan-time checks alonenot 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.
Spacelift
- Users are unlimited and private workers are metered, so deployment concurrency rather than headcount drives the bill, which inverts how most engineering budgets are built and is easy to under-forecast.
- There is no affordable paid entry point. The free tier stops at two users and the next tier is a five-figure commitment with nothing in between.
- Three of the five tiers are quote-only, so a shortlist cannot be costed without entering a sales process with each vendor on it.
- The self-hosted build lags the hosted one, has no public worker pool and lacks the Azure and Google Cloud integrations available in the SaaS product, with OIDC federation offered as the workaround.
- Stacks, Rego policies, Blueprints, Spaces and Spacelift-managed state are proprietary constructs, so leaving means rebuilding the orchestration layer rather than pointing it at a different runner.
Pricing, plan by plan
Cosign
Free- CosignFree
- Apache-2.0
- Public Sigstore infrastructure free to use
- No usage limits published
Spacelift
Free- FreeFree
- Two users
- Public workers only
- No private workers
- Starter Plus$undefined/year
- Unlimited users
- Two public workers
- One to two private workers
- Business$undefined/year
- Unlimited users
- Three private workers
- Quoted
- Enterprise$undefined/year
- Unlimited users
- Five to thirty private workers
- Self-hosted option
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 Spacelift if
- You need multi-tool orchestration.
- You want to start without paying.
- You work on Web, Self-hosted, Cloud.
- You also want policy as code.
Questions people ask
- Is Cosign or Spacelift better?
- Neither clearly leads. Cosign starts at Free and Spacelift at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Cosign or Spacelift?
- Cosign starts at Free and Spacelift at Free.
- Does Cosign or Spacelift run on more platforms?
- Cosign runs on macOS, Linux, Windows, Docker. Spacelift runs on Web, Self-hosted, Cloud.
- 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 Spacelift is typically brought in for.
- What can Cosign do that Spacelift cannot?
- Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations. Spacelift covers Multi-tool orchestration, Policy as code, Private workers, Spaces.
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.
Spacelift: How is Spacelift priced?
By tier and by private worker count rather than per user. Users are unlimited on every paid plan. The published figure on the pricing page carries no period label, and the FAQ describes the tier as an annual subscription, so confirm the period in writing.
Cosign: Is signing alone enough?
No. Verification is a command somebody runs. Without an admission controller enforcing it, an unsigned image still runs.
Spacelift: Does it support OpenTofu?
Yes, and Spacelift sponsors the OpenTofu project, which is a substantive hedge for anyone avoiding Terraform under the Business Source Licence.
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.
Spacelift: Is there a self-hosted version?
Yes, described as carrying Enterprise functionality, but it is priced on request and lags the hosted product on cloud integrations.
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.
Spacelift: Why not just use the CI system we already have?
That is the real comparison. General purpose CI handles state, drift, approval gates and concurrency control for infrastructure poorly, and whether that is worth a five-figure floor depends on how much infrastructure change your organisation actually ships.
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.
Spacelift: What happens to our pipelines if we leave?
They do not port. Rego policies, Blueprints, Spaces and managed state are Spacelift constructs and the orchestration has to be rebuilt elsewhere.
Related pages
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