Cybersecurity · head to head
Cosign vs OWASP ZAP
Cosign
Cybersecurity
Signs and verifies container images and artifacts, with or without managing keys
- From
- Free
- Rated
- -
OWASP ZAP
Cybersecurity
Free, open-source web application scanner and intercepting proxy, now governed by the Software Security Project.
- From
- Free
- Rated
- -
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.; OWASP ZAP authenticated scanning of modern single-page applications is the hard part and ZAP makes you build it by hand: session handling, token refresh and login scripts are configured per application, and a misconfigured session means the scanner logs itself out and reports a clean result for pages it never reached.
- They diverge on capability: Cosign covers Keyless signing, OWASP ZAP covers Intercepting proxy.
- Prices and features above were last checked on 31 August 2026.
Where they differ
Only the attributes on which Cosign and OWASP ZAP actually diverge.
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 OWASP ZAP
- Intercepting proxy
- Passive scanner
- Active scanner
- AJAX spider
- Automation Framework
- Headless daemon and REST API
- Docker images
- Add-on marketplace
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 OWASP ZAP
- Attaching a signed bill of materials to a release so consumers can verify its provenancenot OWASP ZAP
- Meeting a customer or regulatory requirement for signed artifactsnot OWASP ZAP
- Verifying third-party images before they enter an internal registrynot OWASP ZAP
OWASP ZAP
- Adding a baseline security scan to every application's pipeline where per-target commercial licensing would limit coverage to a handfulnot Cosign
- Manual penetration testing that needs an intercepting proxy, request replay and fuzzing without a paid licence per testernot Cosign
- Teaching developers what an attack against their own endpoint looks like, using a tool they can install themselvesnot Cosign
- Pre-release regression scanning of an internal application that would never justify a commercial DAST subscriptionnot 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.
OWASP ZAP
- Authenticated scanning of modern single-page applications is the hard part and ZAP makes you build it by hand: session handling, token refresh and login scripts are configured per application, and a misconfigured session means the scanner logs itself out and reports a clean result for pages it never reached.
- There is no support contract in the product, so when a scan breaks the day before a release the escalation path is a GitHub issue and a community chat, which is not an answer that satisfies a delivery manager or an auditor who wants a named responsible party.
- Active scanning sends genuine attack traffic, so it can create records, trigger emails, exhaust rate limits or destabilise a fragile environment, and pointing it at production without prior agreement produces an incident rather than a test result.
- Output needs triage: passive rules generate large volumes of low-severity informational findings about headers and cookie flags that bury the few results that matter, and a team without someone tuning the rule set stops reading the report within a few sprints.
- As a dynamic scanner it can only test what it can reach, so authorisation flaws between accounts, business logic abuse and anything behind an undiscovered endpoint go unreported, and a passing ZAP scan is evidence of nothing more than the absence of the classes of bug it looks for.
Pricing, plan by plan
Cosign
Free- CosignFree
- Apache-2.0
- Public Sigstore infrastructure free to use
- No usage limits published
OWASP ZAP
Free- Free & Open SourceFree
- Full functionality
- Active & passive scanning
- Spider
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 OWASP ZAP if
- You need intercepting proxy.
- You want to start without paying.
- You work on Desktop, Cli, Api.
- You also want passive scanner.
Questions people ask
- Is Cosign or OWASP ZAP better?
- Neither clearly leads. Cosign starts at Free and OWASP ZAP at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
- Which is cheaper, Cosign or OWASP ZAP?
- Cosign starts at Free and OWASP ZAP at Free.
- Does Cosign or OWASP ZAP run on more platforms?
- Cosign runs on macOS, Linux, Windows, Docker. OWASP ZAP runs on Desktop, Cli, Api.
- 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 OWASP ZAP is typically brought in for.
- What can Cosign do that OWASP ZAP cannot?
- Cosign covers Keyless signing, Key and KMS signing, Registry-native storage, In-toto attestations. OWASP ZAP covers Intercepting proxy, Passive scanner, Active scanner, AJAX spider.
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.
OWASP ZAP: Is it still called OWASP ZAP?
The project left OWASP in August 2024 and is now governed by the Software Security Project, with core development sponsored by Checkmarx. The tool is now just ZAP, though most existing documentation, courses and search results still use the OWASP name.
Cosign: Is signing alone enough?
No. Verification is a command somebody runs. Without an admission controller enforcing it, an unsigned image still runs.
OWASP ZAP: Is it free for commercial use?
Yes. It is Apache 2.0 licensed, with no per-application, per-scan or per-user cost, and it can be used and modified commercially without a licence agreement.
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.
OWASP ZAP: Can it replace a penetration test?
No. It automates checks for known vulnerability classes against endpoints it can reach. It does not reason about business logic, chain findings into an attack, or test authorisation between accounts, which is most of what a tester actually does.
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.
OWASP ZAP: Does it run in CI?
Yes, through the official Docker images and the Automation Framework, which defines scan jobs in YAML so configuration lives in the repository. A baseline passive scan is the usual starting point because it is fast and non-intrusive.
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.
OWASP ZAP: How does it compare to Burp Suite?
Burp Suite Professional is the more polished manual testing tool and has a stronger scanner and extension ecosystem, but it is licensed per tester and Burp Suite Enterprise per target. ZAP is the better fit where cost per target is the binding constraint; many teams use both.
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