Best Free Code Quality Tools

AI-powered code review tool for GitHub/GitLab/Bitbucket. Free tier: basic PR summarization and reviews in IDE on unlimited public and private repositories, with a 14-day Pro trial included (no credit card). Paid Pro is $24/user/month billed annually and adds detailed reviews with 5 reviews/hour; Pro Plus adds 10 reviews/hour. Free-for-open-source may still apply but is no longer prominently featured on the pricing page. Best for unlimited usage needs.

Advanced static analysis for automatically finding runtime errors in JavaScript code, free for Open Source Best for open source projects.

Website performance testing — Lighthouse-based reports with Core Web Vitals, waterfall charts, and optimization recommendations. Free account: testing from Seattle and London, dashboard with filters and tags, daily/weekly/monthly monitoring, e-mail alerts, and 1-month CrUX history. GTmetrix states no on-demand test or monitored-slot quantity for the free account; the cheapest paid plan (Lite, $5.99/mo) lists 50 monthly on-demand tests and 1 monitored slot.

Automate performance tracking in your CI pipelines. Catch performance regressions before deployment, thanks to precise and consistent metrics. Free forever for Open Source projects. Best for open source projects.

Code Quality for Go projects, free for Open Source Best for open source projects.

Static code analysis for Java, C/C++, C# and JavaScript, free for Open Source Best for open source projects.

Continuous inspection platform, free for Open Source Best for open source projects.

DeepSource continuously analyzes source code changes, finding and fixing issues categorized under security, performance, anti-patterns, bug-risks, documentation, and style. Native integration with GitHub, GitLab, and Bitbucket.

Code review for GitHub repositories, free for public or personal repos. Best for personal projects.

Programming language aware diff for GitHub pull requests and commits, free for public repositories

The #1 static code analyzer for Postgresql optimization. Performance, security, and architect database issues automatic detection service

Surfaces `TODO` comments (and other markers) to identify areas of code worth returning to for improvement.

Superseded: As of 2026-08-28, pullflow.com reads: The Free plan is $0 forever for open source projects, startups, and small dev teams. It includes unlimited public repos, unlimited public users, and 5 private-repo users. We are not publishing our stored Pullflow terms beside it — our own pricing change record, discovered 2026-08-28, names them as the previous ones. Read what we recorded ↓ Note — discovered 2026-08-28: The free tier now has limits: unlimited public repos, unlimited public users, and 5 private repo users. Source ↗

Instantly find the differences between two blocks of code. Completely free to use.

Automated Code Review for Git. The free version includes unlimited users, public repositories, and one private repo. Best for unlimited usage needs.

Automated Infrastructure as Code review tool for DevOps integrates with GitHub, Bitbucket, and GitLab (even self-hosted). In addition to standard languages, it also analyzes Ansible, Terraform, CloudFormation, Kubernetes, and more. (open-source free)

Comments on GitHub commits about code quality, free for Open Source Best for open source projects.

Test coverage tracking — displays coverage reports with line-by-line detail, PR comments, and badge embeds. Free for open source repos with unlimited public repos. Supports 22+ languages Best for open source projects and unlimited usage needs.

AI-powered code review assistant. The free plan has a limit of 25,000 monthly tokens (~10 PRs).

Automated code reviews for PHP, Python, Ruby, Java, JavaScript, Scala, CSS, and CoffeeScript — free for open source. 4 users, 7 repos on free plan. Static analysis, security patterns, duplication detection, code complexity metrics Best for open source projects.