# GitHub Pixel Diff

> Adds a pixel-level image diff to the image viewer on GitHub and GitLab — next to 2-up, Swipe and Onion Skin.

Canonical page: [https://chrome-stats.com/d/github-pixel-diff](https://chrome-stats.com/d/github-pixel-diff)

## Overview

- **ID:** `github-pixel-diff`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** illusionist nemo
- **Category:** web-development
- **Daily users:** 3
- **Version:** 0.19.0
- **Last updated:** 2026-10-15
- **First published:** 2026-09-08
- **Size:** 112 KB
- **Data as of:** 2026-10-17
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/github-pixel-diff/)
- **Website:** [https://github.com/Nemo-Illusionist/gh-pixel-diff](https://github.com/Nemo-Illusionist/gh-pixel-diff)
- **Privacy policy:** [https://addons.mozilla.org/firefox/addon/github-pixel-diff/privacy/](https://addons.mozilla.org/firefox/addon/github-pixel-diff/privacy/)

## Description

GitHub and GitLab both show you two versions of an image. Neither shows you what changed between them.

Pixel Diff adds a fourth mode next to 2-up, Swipe and Onion Skin — in GitHub's image viewer and in GitLab's merge requests. It compares the two images pixel by pixel, paints every difference red, and crops the result to the area that actually changed — so a three-pixel shift in a long screenshot is a three-pixel shift you can see, not a picture you have to hunt through.
<ul><li>A threshold slider: raise it to ignore compression noise, lower it to catch everything.</li><li>Before / after / diff, and all three side by side, sharing one scale and one crop.</li><li>Images that changed size are aligned and compared anyway.</li><li>SVG and other vector images are rasterised before comparison.</li><li>Works on the images the site has already loaded — nothing is uploaded anywhere.</li><li>A GitLab of your own: add its address on the settings page, grant access, and the mode appears in that instance too.</li><li>No merge request at hand? Two images of your own compare the same way at <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/a53a5cbfa41eefc7c2cc396a8fe49facd2aa3bbfb8e142bccf20a005a77374dd/https%3A//nemo-illusionist.github.io/gh-pixel-diff/" rel="nofollow">https://nemo-illusionist.github.io/gh-pixel-diff/</a></li></ul>
The comparison runs in your browser, in a background thread. The extension has no server, collects nothing, and sends nothing.

Open source: <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/525bd9e0548048ab4ab67b50ddf9c36dd6c2b78503503bcb92e84c83df9b36e6/https%3A//github.com/Nemo-Illusionist/gh-pixel-diff" rel="nofollow">https://github.com/Nemo-Illusionist/gh-pixel-diff</a>

## Rankings

- #60,626 — Overall
- #161 — github

## Permissions and access

### Permissions

- `storage`
- `scripting`

### Host permissions

- `https://viewscreen.githubusercontent.com/*`
- `https://gitlab.com/*`

### Content script matches

- `viewscreen.githubusercontent.com`
- `gitlab.com`

## Safety

- **Risk impact:** Moderate risk impact
- **Risk likelihood:** High risk likelihood

### Analysis details

- Request access to the following domains: viewscreen.githubusercontent.com, gitlab.com
- This extension was recently updated in the past month. New updates may not be stable or safe.

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

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Source: [Chrome-Stats](https://chrome-stats.com/d/github-pixel-diff)