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Cybersecurity · head to head

OWASP ZAP vs Swagger UI

OWASP ZAP logo

OWASP ZAP

Cybersecurity

Free, open-source web application scanner and intercepting proxy, now governed by the Software Security Project.

From
Free
Rated
-
Full reviewWebsite
Swagger UI logo

Swagger UI

Developer Tools

Interactive API documentation generated from OpenAPI specs

From
Free
Rated
-
Full reviewWebsite

The short version

  • Each has a real cost: 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.; Swagger UI only as good as the specification: a thin OpenAPI file produces thin documentation
  • They diverge on capability: OWASP ZAP covers Intercepting proxy, Swagger UI covers OpenAPI rendering.
  • Prices and features above were last checked on 30 August 2026.

Where they differ

Only the attributes on which OWASP ZAP and Swagger UI actually diverge.

Attributes where OWASP ZAP and Swagger UI differ
AttributeOWASP ZAPSwagger UI
Pricing modelfreeOpen source, no licence fee
PlatformsDesktop, Cli, ApiWeb, Self-hosted, Docker
CategoryCybersecurityDeveloper Tools
Founded2001Unknown

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 OWASP ZAP

  • Intercepting proxy
  • Passive scanner
  • Active scanner
  • AJAX spider
  • Automation Framework
  • Headless daemon and REST API
  • Docker images
  • Add-on marketplace

Only in Swagger UI

  • OpenAPI rendering
  • Try it out
  • Schema display
  • Self-hostable

What people use each for

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

OWASP ZAP

  • Adding a baseline security scan to every application's pipeline where per-target commercial licensing would limit coverage to a handfulnot Swagger UI
  • Manual penetration testing that needs an intercepting proxy, request replay and fuzzing without a paid licence per testernot Swagger UI
  • Teaching developers what an attack against their own endpoint looks like, using a tool they can install themselvesnot Swagger UI
  • Pre-release regression scanning of an internal application that would never justify a commercial DAST subscriptionnot Swagger UI

Swagger UI

  • Publishing API documentation that stays in step with the specificationnot OWASP ZAP
  • Letting developers try endpoints before writing any client codenot OWASP ZAP
  • Internal API discovery across teamsnot OWASP ZAP

Where each one falls short

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

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.

Swagger UI

  • Only as good as the specification: a thin OpenAPI file produces thin documentation
  • Default presentation is dated compared with modern documentation tools
  • Large specifications render slowly and become hard to navigate
  • Try it out against production needs care with authentication and CORS, and is often disabled as a result

Pricing, plan by plan

OWASP ZAP

Free
  • Free & Open SourceFree
    • Full functionality
    • Active & passive scanning
    • Spider

Swagger UI

Free
  • Swagger UIFree
    • Full functionality
    • Commercial use permitted
    • Community support

Which should you pick?

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.
OWASP ZAP review

Choose Swagger UI if

  • You need openapi rendering.
  • You want to start without paying.
  • You work on Web, Self-hosted, Docker.
  • You also want try it out.
Swagger UI review

Questions people ask

Is OWASP ZAP or Swagger UI better?
Neither clearly leads. OWASP ZAP starts at Free and Swagger UI at Free, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, OWASP ZAP or Swagger UI?
OWASP ZAP starts at Free and Swagger UI at Free.
Does OWASP ZAP or Swagger UI run on more platforms?
OWASP ZAP runs on Desktop, Cli, Api. Swagger UI runs on Web, Self-hosted, Docker.
Can I use OWASP ZAP for free?
Both have a free tier, so you can try either at no cost before committing.
What is OWASP ZAP best used for?
OWASP ZAP is most often used for adding a baseline security scan to every application's pipeline where per-target commercial licensing would limit coverage to a handful, manual penetration testing that needs an intercepting proxy, request replay and fuzzing without a paid licence per tester, teaching developers what an attack against their own endpoint looks like, using a tool they can install themselves, pre-release regression scanning of an internal application that would never justify a commercial dast subscription. Of those, adding a baseline security scan to every application's pipeline where per-target commercial licensing would limit coverage to a handful and manual penetration testing that needs an intercepting proxy, request replay and fuzzing without a paid licence per tester are not what Swagger UI is typically brought in for.
What can OWASP ZAP do that Swagger UI cannot?
OWASP ZAP covers Intercepting proxy, Passive scanner, Active scanner, AJAX spider. Swagger UI covers OpenAPI rendering, Try it out, Schema display, Self-hostable.

Answered from the vendors’ own pages

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.

Swagger UI: Is Swagger UI free?

Yes, open source under the Apache 2.0 licence. SmartBear sells commercial SwaggerHub separately.

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.

Swagger UI: What is the difference between Swagger and OpenAPI?

OpenAPI is the specification format; Swagger is the toolset around it, including Swagger UI. The specification was renamed from Swagger to OpenAPI in 2016.

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.

Swagger UI: Can Swagger UI make real API calls?

Yes, through its try-it-out control, though authentication and CORS configuration often mean it is disabled for production APIs.

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.

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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