Free AI code review tools for open source projects (2026)

Free AI code review tools for open source, compared

Six free options cover public repositories, from install-and-go to self-hosted. The biggest differences are whether you apply and how many reviews a project gets.

The six free options one by one

The first two work as soon as they’re installed; the next three need an application or an invitation; the last runs on your own infrastructure.

1. HeyDeer

HeyDeer reviews public repositories free up to a fair-use limit, with no application, and popular public repositories can run more reviews at once than the Free plan includes. Each review reads the change against the whole repository, checks every finding before posting it, and follows the project’s REVIEW.md and AGENTS.md. HeyDeer has the highest precision in ReviewBench’s default view (a Deep review), so maintainers spend their time on comments worth acting on.

Best for: projects of any size that want reviews on every pull request, including contributors’ forks, without an application.

2. CodeRabbit

CodeRabbit gives public repositories its Team features free, with no credit card. Pull request reviews are rate-limited to between 1 and 10 per developer per hour depending on the repository’s stars, and repositories under 10 stars trigger reviews manually. It also reviews on GitLab, Bitbucket and Azure DevOps.

Best for: established projects outside GitHub, or teams that want the same reviewer in the IDE. CodeRabbit alternatives

3. Greptile

Greptile reviews public GitHub and GitLab repositories with an OSI-approved license free once the project applies; projects with 50 or more stars are approved automatically. Its pricing page describes the program as for qualified non-commercial projects.

Best for: non-commercial projects with 50+ stars and large codebases. Greptile alternatives

4. Qodo

Qualified open source projects can apply to Qodo for Open Source for free access, then install Qodo’s GitHub app on the repositories they choose. Qodo reviews on GitHub, GitLab, Bitbucket and Azure DevOps, with Gerrit on Enterprise.

Best for: projects that mirror their code across several Git hosts.

5. GitHub Copilot

GitHub gives Copilot Pro free to maintainers of popular open source repositories and reevaluates eligibility every month. Copilot Pro includes pull request reviews on GitHub, paid from its monthly AI Credits, along with Copilot’s coding features.

Best for: maintainers who already qualify and want review inside GitHub’s own interface. GitHub Copilot code review

6. PR-Agent

PR-Agent is an MIT-licensed reviewer you run yourself as a GitHub Action, CLI, Docker container or webhook service, with your own key for OpenAI, Anthropic, Google, DeepSeek, Mistral or a local model. It’s community-maintained and separate from Qodo’s hosted product.

Best for: projects that need to choose the model or keep code on their own servers.

Hosted vs self-hosted: what free costs you

A hosted reviewer pays for the model itself; a self-hosted one is free software that runs on your model bill. For an open source project, the bigger difference is who can trigger a review.

GitHub’s documentation states that a workflow triggered from a forked repository receives GITHUB_TOKEN as its only secret. A self-hosted AI reviewer running as a GitHub Action therefore loses its model API key on contributors’ fork pull requests, where outside contributions arrive.

The usual workaround, the pull_request_target trigger, runs with the base repository’s secrets, and GitHub warns about its security risks when a workflow builds or runs code from the pull request. A hosted GitHub App such as HeyDeer or CodeRabbit sidesteps both: it reads the pull request through its own installation and calls the model with its own credentials, so fork pull requests get the same review as maintainers’ branches.

Which free option fits your project

• A new or small project: HeyDeer reviews from the first pull request, whatever the star count.
• A popular project with many outside contributors: a hosted GitHub App (HeyDeer or CodeRabbit) with fork pull requests included; check whether your maintainers also qualify for free Copilot Pro.
• A non-commercial project with 50+ stars: Greptile’s program approves it automatically.
• Code that has to stay on your servers: PR-Agent with a model you host, reviewing maintainers’ branches.

To weigh accuracy as well as price, see the AI code review tools ranked by precision, or try two reviewers on the same pull requests with the evaluation guide. Paid plans for private repositories are compared in AI code review pricing.

How to add free AI code review to an open source repository

With HeyDeer, setup takes a few minutes; in a GitHub organization, an owner approves the installation:

1. Sign in with GitHub and choose the account or organization that owns the project.
2. On GitHub, select the public repositories for HeyDeer to review.
3. Include contributors’ pull requests: in Workspace settings → Review rules, add Fork to the PR source filter. Automatic reviews start with same-repository pull requests only.
4. Add a REVIEW.md with the project’s conventions, so reviews hold contributors to the same standards as maintainers.
5. Comment @heydeer review on any open pull request to review it right away.

For a project with outside contributors, the most useful setting is the fork filter: contributors’ pull requests are the ones maintainers know least, and an AI review that arrives first gives the maintainer a list of specific issues to check before reading the change.

Sources

1. HeyDeer plans: public repositories
2. CodeRabbit pricing
3. CodeRabbit plans and rate limits
4. Greptile for open source
5. Qodo for Open Source
6. Free access to GitHub Copilot Pro
7. GitHub Copilot plans
8. PR-Agent on GitHub
9. GitHub Docs: using secrets in GitHub Actions
10. GitHub Docs: events that trigger workflows