SAST analyzes your app's code without running it. DAST tests the app while it runs. They find different classes of problems, so they are complementary, not competing. For most mobile teams the practical order is SAST first, because static analysis needs only the code and drops straight into your pipeline, while dynamic testing needs a running build to exercise. Here is the difference that actually drives the decision.
What is SAST in mobile app security testing?
SAST stands for Static Application Security Testing. It analyzes an app's source or compiled code without executing it. NIST defines a static code analyzer as "a tool that analyzes source code without executing the code." (NIST glossary) OWASP's Mobile Application Security Testing Guide (MASTG) puts it in mobile terms: SAST "involves examining an app's components without executing them, by analyzing the source code either manually or automatically." (OWASP MASTG) Because it only needs the code, SAST can run as early as the editor; OWASP notes "SAST tools can be added into your IDE." (OWASP)
What is DAST in mobile app security testing?
DAST stands for Dynamic Application Security Testing. It analyzes the app while it runs. NIST defines a dynamic code analyzer as "a tool that analyzes computer software by executing programs built from the software being analyzed... and observing its behavior." (NIST glossary) In mobile terms, OWASP MASTG says DAST "involves examining the app during runtime," and adds that it "usually doesn't provide the information that static analysis provides, but it is a good way to detect interesting elements (assets, features, entry points, etc.) from a user's point of view." (OWASP MASTG)
SAST vs DAST: what is the core difference?
One question separates them: are you inspecting the code, or watching the app run? Everything else follows from that.
| SAST (static) | DAST (dynamic) | |
|---|---|---|
| What it analyzes | Source or binary code, not running | The app while it executes |
| When it can run | As soon as code exists (IDE, CI) | Once there is a runnable build |
| Strength | Early, code-level, points at the line | Real runtime behavior, a user's-eye view |
| Characteristic blind spot | Noise: false positives if untuned | Misses code paths it never exercises |
| Mobile reference | OWASP MASTG | OWASP MASTG |
The two blind spots mirror each other, which is the whole reason both methods exist. OWASP states DAST "usually doesn't provide the information that static analysis provides," (OWASP MASTG) while manual static review "is very good for identifying vulnerabilities in the business logic, standards violations, and design flaws," scenarios "unlikely to be detected by any automatic code analysis tool." (OWASP MASTG)
Does SAST or DAST produce more false positives?
The documented drawback sits with automated SAST: OWASP notes such tools "may produce many false positives, particularly if they are not configured for the target environment." (OWASP MASTG) No credible source attaches a specific false-positive rate to either method, so treat any precise percentage you see with suspicion. DAST's mirror weakness is omission rather than noise: it only reports on what it actually exercises at runtime. The practical lesson is that raw finding count is not a quality signal; triaged true positives are.
Which should you run first, SAST or DAST?
For a typical mobile team, run SAST first. This is a sequencing judgment, not an OWASP or NIST rule, and it rests on one structural fact: static analysis needs only the code, so it integrates into the editor and CI immediately and can gate every commit, while dynamic testing cannot start until there is a build to run. SAST is therefore the cheapest, earliest, most automatable feedback loop, and it makes a natural first security gate. DAST comes online a step later, against running builds. Neither standard says one matters more than the other; the order is purely about when each technique can run.
Why do mature programs run both?
Because each technique's blind spot is the other's strength. A serious mobile program runs SAST in the pipeline and DAST against running builds, then verifies the results against OWASP MASVS requirements using MASTG test cases. (OWASP MASVS) Two further layers sit on top rather than replacing this pair: interactive testing (IAST) instruments the running app to combine the static and dynamic views from the inside, and a manual penetration test adds human depth that neither automated method reaches.
How does this map to OWASP MASVS and MASTG?
MASVS, the Mobile Application Security Verification Standard, is "the industry standard for mobile app security." (OWASP MASVS) It sets the requirements to verify, the "what." The MASTG is the companion testing guide, the "how," and it is the source of the SAST and DAST definitions used here. A clean way to hold the relationship: MASVS lists the security requirements, MASTG provides the techniques to verify them, and SAST and DAST are the static and dynamic methods inside that guide.
The verdict: SAST vs DAST for mobile
Inspect the code, or watch it run. SAST reads your code without executing it and belongs early, on every commit; DAST exercises the running app and belongs once there is a build to test. Lead with SAST because it is cheaper and earlier to stand up, add DAST as soon as you have something to run, and treat them as partners rather than alternatives. The honest framing is not which one is better, but when each one can run.
Sources
NIST glossary, static code analyzer (NISTIR 8011 Vol. 4). https://csrc.nist.gov/glossary/term/static_code_analyzer
NIST glossary, dynamic code analyzer (NISTIR 8011 Vol. 4). https://csrc.nist.gov/glossary/term/dynamic_code_analyzer
OWASP MASTG, Mobile App Security Testing (SAST and DAST definitions). https://mas.owasp.org/MASTG/0x04b-Mobile-App-Security-Testing/
OWASP MASVS, Mobile Application Security Verification Standard. https://mas.owasp.org/MASVS/
OWASP Community, Source Code Analysis Tools (SAST and DAST acronyms). https://owasp.org/www-community/Source_Code_Analysis_Tools
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