SAST analyses source code without running it, so it finds certain flaw patterns early and points at the line. DAST attacks the running application from outside, so it finds problems that only exist at runtime, like misconfiguration. They see different things. Use both, at different stages, and feed findings to one backlog.
What does SAST see?
OWASP describes source code analysis tools, also called static application security testing tools, as tools that analyse source code or compiled code to find security flaws, and notes they can sit in your IDE. Their strengths, per OWASP: they scale well and can be run repeatedly, such as in nightly builds or continuous integration; they identify well known issues like buffer overflows and SQL injection; and their output highlights the file, location and line number.
The weaknesses are just as stated. OWASP says automated searches are difficult for authentication problems, access control issues and insecure use of cryptography. It notes current SAST tools can automatically identify only a relatively small percentage of application security flaws, produce high numbers of false positives, frequently cannot find configuration issues because those are not represented in the code, and find it hard to prove that a flagged issue is a real vulnerability.
What does DAST see?
Dynamic testing treats the application as a black box. It sends requests to a running instance and watches responses. The OWASP Web Security Testing Guide is the reference for how web testing is done. Because it runs against a deployed build, DAST sees what static analysis cannot: deployed configuration, missing security headers, exposed endpoints, error messages that leak detail and behaviour that emerges from how components fit together.
Its limits mirror SAST. It needs a running, reachable app, so it comes later. Coverage depends on what it can discover and log in to. It tells you that a URL misbehaves, not which line of code to change.
Where does each fit in the lifecycle?
NIST SP 800-218, the Secure Software Development Framework, has practices on both sides: reviewing and analysing human-readable code, and testing executable code. They map to the two techniques.
Run SAST at the developer's desk and on every pull request, because feedback in minutes is cheap to act on. Run DAST against a staging or preview environment on a schedule and before release, because it needs something deployed. Run the combination again after infrastructure changes, since DAST will catch what a new load balancer or gateway setting exposes.
A constructed example
A team ships a customer portal. SAST flags a query built by concatenating a request parameter; the developer fixes it before merge. Nothing in the code flags that the staging environment's admin path is reachable from the internet without login, because the reverse proxy rules sit in a different repository.
The weekly DAST run finds the open admin path in minutes. Each tool caught something the other could not, and the fix for the second was a proxy change that no code scanner would have flagged.
Why do findings pile up?
Two tools means two lists, with duplicates and noise. Teams that run both without a plan end up ignoring both. Agree on severity, deduplicate by location, and decide which findings block a merge or a release and which become backlog items. Reachability information, which asks whether vulnerable code can actually be hit, helps a lot with ranking.
Safeguard offers SAST and DAST alongside dependency scanning with reachability analysis and policies and gates, so findings from code, dependencies and the running app can land in one place and be enforced as release rules. Whatever you use, treat results as leads to confirm, as OWASP's note on false positives suggests.
How to check or apply this
- Run SAST in the IDE and on every pull request, and fail the build only on high confidence findings at first.
- Stand up a staging environment that mirrors production configuration.
- Run DAST there with authenticated scans, on a schedule and before each release.
- Combine results into one backlog with owners and due dates.
- Add dependency scanning, since neither SAST nor DAST covers third party libraries well.
- Tune rules each month to cut false positives.
- Add manual testing for access control and business logic, which both tools struggle with.
Quick check
Can I use only SAST or only DAST?
You can, but you will miss what the other sees. SAST misses runtime configuration problems. DAST misses code paths it cannot reach.
Do these tools replace penetration testing?
No. Automated tools find known patterns. Skilled testers find access control and business logic flaws that tools often miss.
Sources
Last reviewed: 18 October 2026.
