API security testing is a kind of dynamic testing, so it overlaps with DAST, but the focus differs. Classic DAST crawls pages and forms of a web application. API testing works from endpoint definitions and concentrates on authorization, object access, data exposure and abuse of business flows.
Definitions
DAST scans a running web application from the outside, according to OWASP, looking for issues such as cross-site scripting, SQL injection and insecure server configuration.
API security testing sends requests to API endpoints, often guided by a description such as an OpenAPI file, and checks how the service behaves when roles, identifiers and inputs are changed.
Where they differ
| Web DAST | API security testing | |
|---|---|---|
| Entry point | Pages, links, forms | Endpoint list, spec, recorded traffic |
| Typical clients | Browsers | Mobile apps, scripts, other services |
| Strong on | Injection, headers, session handling | Broken authorization, excessive data, missing limits |
| Needs | A reachable site | Valid tokens for several roles |
| Common gap | Endpoints not linked from pages | Endpoints missing from the spec |
Why a separate list exists
OWASP published a distinct API Security Top 10, with a 2023 edition that is the second after the 2019 list. Its introduction says the list does not replace the other OWASP Top 10 projects, and that teams with an app backed by an API should review both.
A simple test pattern
- Obtain tokens for at least two ordinary users and one admin.
- For each endpoint that takes an identifier, request another user's object with your token. A success is a serious finding.
- Compare responses with what the screen shows. Extra fields in the response are data exposure.
- Send rapid repeated requests to see whether limits exist.
- Try methods and versions that the spec does not list.
Common mistakes
A frequent oversight is testing only with one account. Authorization bugs appear when you switch identity, so a single login proves little. Another is skipping non production clients such as mobile apps, which may call endpoints that the web front end never uses. Capture traffic from every client type when you build the endpoint list. Finally, retest after fixes with the same two accounts, so you know the specific access was blocked and not merely hidden.
Try it yourself
Click through it at your own pace, or open it full screen.
Look for findings that depend on who is calling, not only on what is sent.
Quick check
Can one tool do both?
Some scanners handle web pages and APIs. Check whether it can import a spec and use several credentials.
Do I need a spec to test an API?
No, recorded traffic works too, but a spec gives better coverage.
Where Safeguard fits
Safeguard provides SBOM and dependency scanning for the libraries behind your APIs, plus policy gates. Try the free scan.
Sources
Last reviewed: 19 October 2026.
