SAST analyzes source code without running it, DAST attacks a running application from the outside, and IAST uses sensors inside the application while tests exercise it. SAST fits early in development, DAST fits a deployed test environment, and IAST fits teams with good automated tests.
Key takeaways
- SAST needs source code. DAST needs a running app. IAST needs a running app with sensors and traffic.
- Each finds different bugs, so they complement each other instead of replacing one another.
- Most small teams start with SAST in pull requests, then add DAST on a staging site.
- IAST coverage depends on what your tests actually exercise.
What is SAST?
SAST is white-box testing that examines code without executing it. OWASP describes static analysis as examining code without running the program, and says it helps find security vulnerabilities, programming errors and coding standard violations. It points to a file and line, which makes fixes easy to locate. OWASP's community page also lists high false positives and difficulty confirming exploitability as weaknesses.
What is DAST?
DAST is black-box testing of a running application. OWASP says it injects malicious payloads into a running app and can reveal issues such as SQL injection and cross-site scripting. It also finds input and output validation problems, authentication issues and server configuration mistakes, and it needs no source code. The app must be deployed, so it runs later in the cycle.
What is IAST?
IAST tests an application from the inside while it runs. OWASP says it relies on sensor modules, libraries included in the application, which monitor behavior during interactive testing driven by automated tests or a human tester. Sensors can see data and control flow, configuration and back-end connections. Coverage follows the interactions that run, so thin test suites produce thin results.
How do they compare?
| SAST | DAST | IAST | |
|---|---|---|---|
| Needs source code | Yes | No | Sensors are added to the app |
| Needs a running app | No | Yes | Yes |
| Typical stage | Pull request, build | Staging or test environment | QA or test run |
| Points to code line | Yes | Not directly | Yes, per OWASP sensors see code and data flow |
| Common limit | False positives, no runtime view | Only sees what is exposed at runtime | Only sees code that tests reach |
Which should I adopt first?
Adopt SAST first if you have source in a repository and want feedback in pull requests. Add DAST when you have a stable staging deployment. Consider IAST once your integration tests are solid. Our interactive SAST demo shows what a code scan report looks like.
Click through it at your own pace, or open it full screen.
What about dependencies?
None of the three reads your package manifest for known vulnerable libraries. That is software composition analysis. Try the free in-browser dependency scan, no login, file stays on your machine, up to 100 dependencies.
Frequently asked questions
Is SAST better than DAST?
Neither is better. They find different problems at different stages, so teams usually use both.
Can DAST replace SAST?
No. DAST cannot see code paths the running app does not expose, and SAST cannot see runtime configuration.
Is IAST the same as DAST?
No. DAST attacks from outside. IAST uses sensors inside the app during testing.
Which is cheapest to start?
SAST, because free tools run on a repository with no deployed environment. See our guide to free SAST tools.
Sources
- OWASP DevSecOps Guideline, SAST: https://owasp.github.io/www-project-devsecops-guideline/latest/02a-Static-Application-Security-Testing
- OWASP DevSecOps Guideline, DAST: https://owasp.github.io/www-project-devsecops-guideline/latest/02b-Dynamic-Application-Security-Testing
- OWASP DevSecOps Guideline, IAST: https://owasp.github.io/www-project-devsecops-guideline/latest/02c-Interactive-Application-Security-Testing
- OWASP Source Code Analysis Tools: https://community.owasp.org/Source_Code_Analysis_Tools
Last reviewed: 19 October 2026.
