Last updated 10 September 2026.
What the extension collects
Nothing. It has no analytics, no telemetry, no crash reporting, and no server of its own. Nothing about you or the pages you visit is sent anywhere.
What it stores
Two kinds of settings, and only settings:
- Your preferences — the diff threshold, whether the outline is drawn, which frame was shown last, and whether the before / after / diff switcher is visible. They are kept by the browser's own extension storage. If you are signed into the browser and have extension sync turned on, the browser may sync them across your devices; that is the browser's mechanism, not ours.
- The permission you grant — held by the browser itself, and revocable at any time from the browser's extension settings.
No image, file name, repository name, URL, or account information is stored.
What it accesses
The extension runs on two addresses:
https://viewscreen.githubusercontent.com/diff/img, the frame
GitHub uses to display image diffs, and https://gitlab.com,
where GitLab renders them on the page itself. There it reads the two images
the site has already loaded and compares them in your browser. It does not
run on github.com pages, does not read your repositories, and
does not touch any other site.
The comparison happens entirely on your machine. The images never leave it.
If you add a GitLab of your own on the settings page, that instance's
address joins the list — you grant it by hand, one host at a time, and revoke
it from the same page or from the browser's own settings. The extension
behaves there exactly as it does on gitlab.com, and on a page
that is not GitLab it does nothing at all.
This page
The comparison page on this site works the same way: the images you drop there are read by the browser and never uploaded. There is no server behind the page — it is a static file on GitHub Pages.
Third parties
None. No data is shared, sold, or transferred to anyone, and no code is loaded from a remote server — everything the extension runs ships inside the package.
Contact
Questions and reports: the issue tracker.