Full-screen overlay
Click View Diff on the pull request page. The viewer opens over GitHub, and diffy starts prefetching as the page loads.
Fast code review experience on GitHub, even for large PRs
Open the whole change set, comment inline, and publish your review when you are ready.
Why diffy?
Large diffs hit documented limits and long-standing UI friction. diffy is a dedicated viewer for those reviews.
GitHub
diffy
GitHubDiff too large to display
diffyFetches the PR through the GitHub API and renders it in a dedicated viewer.
GitHubLoad more on every large file
diffyShows full file patches in one continuous scroll.
GitHubFiles changed freezes on medium PRs
diffySyntax highlighting runs in a worker, so the overlay stays responsive.
GitHubHundreds of changed files hit a 406
diffyLoads every file through the paginated files API, then assembles the diff.
GitHubComments split across Conversation and Files changed
diffyInline threads stay on the lines you are reading.
Stay on the PR, or pop it into its own tab.
Install once. Open from the pull request page, or from a link anywhere on GitHub.
Standalone tab
Right-click a PR link or page and choose Open in diffy. Same viewer, in its own tab, including in the background.
Read, queue, then publish from the Review Dock.
Comments stay on the lines you are reading. The dock holds the queue, your summary, and the verdict until you send it to GitHub.
See it in action
Open the whole change set, comment inline, and publish your review when you are ready.
The tools you need while you read the change set
Jump any file, compare image changes, match your editor theme, and tune the layout without leaving the review.
Searchable file tree
Filter as you type and jump to any path, even when the PR has thousands of files.
Layout customization
Side-by-side or unified layout, wrap or scroll, diff indicators, hunk separators, expand or collapse all, and a refresh after new pushes.
Font support
JetBrains Mono, Fira Code, IBM Plex Mono, or a custom family. Numeric size and line-height, with optional ligatures.
Image diffs
Preview image changes inline, then open a lightbox with 2-up, swipe, or onion compare, plus zoom, pan, and blink.
Themes
Pierre themes with separate light and dark picks, plus Auto, Light, or Dark. Syntax highlighting covers 100+ languages.
Your token never leaves the browser.
diffy does not run a backend. Pull request data is fetched from GitHub in your browser. An optional personal access token is stored in browser.storage.local and sent only to the GitHub API. Firefox lists required data collection as none. There is no tracking, telemetry, or analytics in the extension.
Install
Free on Chrome, Firefox, and Edge. Open a pull request and look for View Diff.
FAQ
How do I open a PR in diffy?
On any GitHub pull request page, click View Diff for a full-screen overlay. diffy starts prefetching as the page loads. To open in a separate tab, right-click the PR link or page and choose Open in diffy.
Do I need a diffy account?
No. diffy is a free browser extension. Install it, open a pull request on GitHub, and start reviewing. No sign-up and no subscription.
Can I use diffy on private repos?
Yes. Add a GitHub personal access token in the extension popup. Without a token, only public pull requests are accessible.
Do I need a token just to read a public PR?
No. Public diffs work without a token. You will need one to post comments, and unauthenticated browsing hits GitHub API rate limits sooner.
Which GitHub token should I use?
Any valid token works for diffs, private repos, and posting individual comments. For viewed files and publishing a batch review, use a classic PAT (ghp_) with repo scope, or run gh auth login and paste gh auth token. Fine-grained tokens (github_pat_) do not support that workflow.
Will my team see my comments on GitHub?
Yes. Comments, replies, edits, and review verdicts post through the GitHub API. They show up on the PR and in GitHub notifications, the same as a native review.
Does diffy work on PRs with hundreds of files?
Yes. That is what it is built for. GitHub's Files changed tab slows down or hits API limits on large change sets. diffy loads every changed file through the paginated files API and renders the full diff in one continuous view.
Does diffy replace GitHub?
No. diffy is a review layer on top of GitHub. You stay on github.com, your data stays in your GitHub account, and your team keeps using GitHub as usual.
Is my token safe? Does diffy collect data?
Your token is stored in browser.storage.local inside the extension and is never sent to a diffy server. There is no tracking, telemetry, or analytics. API calls go directly from your browser to GitHub.
Which browsers are supported?
Chrome, Firefox, and Edge, from each browser's extension store. A Safari build is available if you compile from source.