Free static application security testing tools exist and are worth running. They find well-known flaws such as injection and buffer overflows and give file and line numbers. OWASP also lists their limits: many false positives, coverage of only a small share of flaw types, and trouble with code that cannot be compiled.
This guide describes the category. It does not rank products, and you should run any tool on your own code before you decide.
What do SAST tools do well?
OWASP's page on source code analysis tools describes SAST tools as tools that analyse source code or compiled code to find security flaws. They can run in an IDE during development. Strengths it lists: they scale and can run repeatedly, for example in nightly builds or continuous integration. They reliably identify some well-known flaws such as buffer overflows and SQL injection. Their output points to the file, line number and code snippet involved.
OWASP's comparison table includes a licence column, and many entries are marked open source or free, so free options exist across languages. The page also lists commercial tools, and some offer a free tier.
Where do they fall short?
OWASP names these weaknesses.
False positives. High numbers of false positives is listed as a weakness. A tool that reports a hundred findings, of which five matter, costs developer time.
Limited coverage. They can automatically identify only a relatively small percentage of application security flaws. Authentication, access control and insecure cryptography are hard to detect automatically, and configuration issues are often missed.
Build and language needs. Language support is a prerequisite when selecting a tool. OWASP notes that many tools have difficulty analysing code that cannot be compiled, which can require the right libraries, build instructions and all required code.
Proving a finding. It is difficult to confirm that a reported issue is a real vulnerability. Someone has to read the code.
What do free tools usually leave to you?
This is our practical observation, so check each tool's documentation. Paid products often add triage workflow, shared dashboards, single sign-on, support contracts and rule tuning. With a free tool you build or skip those. The cost moves from licence to time.
How do you get value from a free tool?
Start with one repository and a small, well-chosen rule set. Run the tool in CI in report mode and read twenty findings by hand. Mark which are real. Switch off rules that produce mostly noise, keeping a note of why.
Export results in SARIF, an OASIS standard format for static analysis, so you can move between tools or merge results later. Run it in the IDE as well so developers see issues before a pull request.
Gate pull requests only on rules you trust, such as injection patterns with a record of real hits. Everything else becomes a ticket.
Pair SAST with other checks. It looks at your code, not at your dependencies, so add dependency scanning, secrets scanning and testing of the running application.
When should you add more?
Add a second approach when the false positive rate drives people to ignore results, when you need triage across many teams, or when auditors ask for evidence you cannot produce from a folder of reports.
What to do
- Pick a free tool that supports your main language and builds in your CI.
- Run it on one repository in report mode.
- Review twenty findings by hand and note the real ones.
- Disable noisy rules with a recorded reason and review them quarterly.
- Export SARIF and store results with dates.
- Gate on a few trusted rules and add dependency and secrets scanning alongside.
Quick check
Can SAST find all my vulnerabilities?
No. OWASP says it identifies only a relatively small percentage of application security flaws and struggles with authentication, access control and cryptography issues.
Why does code that will not compile confuse the tool?
OWASP notes many SAST tools have difficulty analysing code that cannot be compiled. Fix the build first so the tool has all libraries and sources it needs.
Sources
Last reviewed: 18 October 2026.
