How do I get a git diff from a GitLab merge request?

In GitLab, open your merge request, click the 'Changes' tab, then click 'Download diff' from the three-dot menu. Or run: git fetch origin && git diff origin/main...origin/feature-branch. Via GitLab API: GET /projects/:id/merge_requests/:mr_iid/diffs?unidiff=true.

Can this tool generate GitLab merge request descriptions automatically?

Yes. Paste your MR diff into the tool, choose 'MR Description' mode, and the AI generates a structured description with a summary paragraph, list of changes, and a testing section — ready to paste directly into GitLab's MR description field. Works with any GitLab diff: GitLab.com, self-hosted, or GitLab CI-generated diffs.

Does GitLab have a built-in AI MR summary feature?

GitLab Duo (the premium AI add-on) includes MR summaries in GitLab 16.2+, but only for GitLab Ultimate + Duo Pro subscribers ($39+/user/month). Self-hosted GitLab users require additional configuration. This free tool gives any GitLab user AI MR summaries powered by Claude at pay-per-token rates (typically under $0.001 per MR).

Is my code safe? Does the diff get stored anywhere?

Nothing is stored. The diff goes directly from your browser to Anthropic's API using your own key. No backend, no server, no logging. Your code never touches our infrastructure. Your Anthropic API key is saved only in your browser's localStorage (you can clear it anytime).

What's the cost per GitLab MR summary?

A typical MR diff (300 lines) costs about $0.0003-$0.002 with Claude Haiku or Sonnet — less than a cent. You pay Anthropic directly, pay only for what you use, and there's no subscription. Compare to GitLab Duo which requires Ultimate + Duo Pro at $39+/user/month.

GitLab Merge Request AI Summary — Free MR Description Generator

Paste your GitLab diff (or any git diff)

Anthropic API Key (optional — needed for live AI; skip for demo)

Stored in your browser only. Never sent to our servers. Get a free key →

MR Description

How to get a GitLab MR summary in 3 steps

Get your diff

In GitLab: MR → Changes tab → ··· → Download diff. Or run git diff origin/main...your-branch.

Paste & choose mode

Paste the diff, pick MR Description, Code Review, Commit Message, or Changelog Entry. Add your API key.

Copy into GitLab

Copy the output and paste it directly into your GitLab MR description field or commit form.

AI Diff Summarizer vs GitLab Duo AI — MR Summaries

Feature	AI Diff Summarizer	GitLab Duo AI
Price	~$0.001/MR (Anthropic API)	Requires Ultimate + Duo Pro ($39+/user/mo)
Account requirement	No account needed	GitLab account + paid tier
Works on self-hosted GitLab	Yes — any diff text	GitLab 16.2+ with Duo configured
Works with GitHub/Bitbucket	Yes — git-host agnostic	GitLab only
Model choice	Haiku / Sonnet / Opus	GitLab-managed (model not disclosed)
Changelog generation	Yes — Keep-a-Changelog format	Not available
Native MR UI integration	Copy-paste workflow	Button inside GitLab MR form

Feature

AI Diff Summarizer

GitLab Duo AI

Price

~$0.001/MR (Anthropic API)

Requires Ultimate + Duo Pro ($39+/user/mo)

Account requirement

No account needed

GitLab account + paid tier

Works on self-hosted GitLab

Yes — any diff text

GitLab 16.2+ with Duo configured

Works with GitHub/Bitbucket

Yes — git-host agnostic

GitLab only

Model choice

Haiku / Sonnet / Opus

GitLab-managed (model not disclosed)

Changelog generation

Yes — Keep-a-Changelog format

Not available

Native MR UI integration

Copy-paste workflow

Button inside GitLab MR form

Frequently Asked Questions

How do I export a diff from a GitLab merge request?

Open your merge request → click the Changes tab → click the three-dot (···) menu → select Download diff. Open the downloaded file in any text editor, select all, and paste it here. Alternatively, run git fetch origin && git diff origin/main...origin/your-branch in your terminal for the most reliable result.

Does GitLab have a built-in AI MR description generator?

GitLab Duo includes AI MR summaries in GitLab 16.2+, but only for Ultimate + Duo Pro subscribers (~$39/user/month). Free, Premium, and self-hosted users without Duo Pro don't get this feature. This tool fills that gap at $0 (you pay only Anthropic API tokens, ~$0.001 per MR).

Is this tool private and secure?

Your diff and API key never touch our servers. The page is entirely static HTML/JS — the call to Anthropic's API goes directly from your browser to Anthropic. Your key is stored in localStorage on your machine only. Check the page source if you want to verify.

Does this work with self-hosted GitLab?

Yes. Any standard git diff works regardless of whether you use GitLab.com, a self-hosted Community Edition instance, or GitLab Enterprise. Just copy the diff text using the CLI (git diff) or the GitLab UI and paste it here.

How does the cost compare to GitLab Duo?

GitLab Duo requires Ultimate + Duo Pro at roughly $39/user/month — a 10-person team pays $4,680/year. With this tool, a 300-line MR diff costs ~$0.0003 with Claude Haiku — effectively free regardless of team size. You bring your own Anthropic API key and pay only for what you use.

Can I use this for GitLab CI merge train diffs?

Yes. GitLab merge trains produce standard unified diffs. You can fetch them via the API (GET /projects/:id/merge_requests/:mr_iid/diffs) or by running git diff against the merge ref. Paste the result into this tool to generate MR descriptions or review summaries automatically.