Short answer: most AI code review tools for GitHub are free in one of three ways: free on public repos, a free trial on private repos, or a free monthly allowance that does not expire. If your code is private and you want to try a review today without a card, you need the third kind.
The three kinds of “free”
- Free for open source. Several reviewers review public repositories free. For example, CodeRabbit’s pricing page lists free reviews for public repos. Great for OSS maintainers; it does nothing for a private company repo.
- Free trial. Full features on private repos for a fixed window (CodeRabbit’s is 14 days), then a per-seat plan. Fine if you can evaluate inside the window.
- Free monthly allowance. A small number of reviews or credits every month, private repos included, with no end date. Mergestorm works this way: 30 free credits a month, no card.
None of these is a trick. They suit different people. The mistake is picking a tool, installing it org-wide, and only then finding out your private repos are outside the free tier.
What a useful free review should do
- Comment inline on the diff, not just post a summary. A summary tells you what changed; inline comments tell you what is wrong.
- Read more than the diff. The bugs that hurt are usually a caller the diff did not touch or a config the change forgot.
- Run on every push, so the second commit gets reviewed too, not only the first.
- Stay quiet on nits you did not ask for. A reviewer that posts forty style comments trains people to ignore it.
Run a free AI review on a private repo in 5 minutes
- Start free on Mergestorm and sign in with GitHub or Google. No card.
- Go to Agents and install the Vortex GitHub App on the repo you want reviewed. You can pick single repos; it does not need your whole org.
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Open a pull request, or on one that is already open, comment
@mergestorm-vortex review. - Vortex reads the repo, the diff, and any linked GitHub Issues, then posts inline comments and a GitHub check.
If you want fixes and not only comments, turn on Cyclone: it takes actionable Vortex comments and commits the patch to the PR branch. For a risky change that touches several files, Tempest runs a deeper cross-file review on demand.
Pick a PR that proves something
Do not test a reviewer on a one-line README change. Pick the PR that has been waiting longest, or the one you are least sure about. If the review catches something your team would have caught a day later, you have your answer. If it only posts nits, you have that answer too, and it cost you nothing.
For why an AI first pass matters to your queue in the first place, see code review is the bottleneck. For how long a review should take, see PR review time.