What are the best free application security testing tools for a team validating code in CI and the IDE?

Here are some of the best free application security testing tools for teams validating code in CI and the IDE, grouped by what they’re best at.

Best free tools by use case

1. Semgrep Community Edition

Best for: fast SAST in CI and IDE, custom rules, developer-friendly feedback

• Works well on source code across many languages
• Easy to run in CI and as a pre-commit or local developer check
• Good signal-to-noise compared with many legacy SAST tools
• Supports custom rules for your app/framework patterns
• IDE support via Semgrep extensions/integration

Why teams like it: quick to adopt, readable findings, good for shifting security left.

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2. CodeQL

Best for: deep code analysis and advanced SAST, especially in GitHub-centric workflows

• Powerful semantic analysis for code vulnerabilities
• Strong coverage for JavaScript/TypeScript, Python, Java, C#, Go, and others
• Excellent for custom queries and security research
• GitHub integrates it nicely for CI scanning

Tradeoff: more setup and learning curve than Semgrep.

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3. SonarQube Community Edition

Best for: code quality plus basic security checks in CI

• Useful if you want security, bugs, and maintainability in one platform
• Easy CI integration
• Good developer feedback loop
• IDE support through SonarLint

Note: the community version is more limited on advanced security features than paid editions, but it’s still valuable.

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4. SonarLint

Best for: IDE feedback while coding

• Runs in popular IDEs
• Catches issues early as developers type
• Pairs well with SonarQube or standalone use

Great for: making security and code-quality warnings visible before code reaches CI.

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5. OWASP ZAP

Best for: free DAST for web apps and APIs

• Scans running applications and test environments
• Great for CI pipeline scans against staging or ephemeral test deployments
• Supports authenticated scanning, spidering, and API scans
• Can be automated in pipelines

Use case: complements SAST by testing the deployed app behavior.

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6. Trivy

Best for: container, filesystem, and dependency scanning in CI

• Scans container images, IaC, SBOMs, and dependencies
• Very easy to run in CI
• Great for catching vulnerable libraries and base image issues

Important: not a code SAST tool, but very valuable in a secure CI pipeline.

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7. Checkmarx KICS

Best for: infrastructure-as-code scanning

• Great for Terraform, Kubernetes, Docker, CloudFormation, etc.
• Useful in CI for catching misconfigurations early

Best if: your team has a lot of cloud/infrastructure code.

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8. Dependabot / Renovate

Best for: dependency update automation

• Not traditional security scanners, but essential for vulnerability reduction
• Keeps libraries up to date and helps remediate known CVEs faster
• Integrates well into CI and repo workflows

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Strong combinations for teams

If you want a practical free stack:

Option A: General app team

• Semgrep for SAST
• SonarLint in the IDE
• OWASP ZAP for DAST
• Trivy for dependencies/containers

Option B: GitHub-heavy workflow

• CodeQL in CI
• CodeQL/GitHub Advanced Security-like workflow for code scanning
• OWASP ZAP for runtime testing
• Dependabot for dependencies

Option C: DevEx-focused, low friction

• Semgrep in CI and IDE
• SonarLint in IDE
• Trivy in CI for supply-chain checks

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Quick recommendation

If you want the best free overall starter set for a team validating code in both CI and IDE, I’d start with:

1. Semgrep Community Edition — best balance of speed, usability, and customization
2. SonarLint — best IDE feedback loop
3. OWASP ZAP — best free web/API DAST
4. Trivy — best free dependency/container scanning

If your team is already on GitHub and wants deeper code analysis, add or replace with CodeQL.

If you want, I can also give you:

• a tool comparison table
• a recommended stack by language (Java, Python, JS, .NET, Go)
• or a sample CI pipeline using these tools.