PixelPerfect CSS Diff
PixelPerfect CSS Diff is a standalone Chrome extension for frontend visual QA.
It is useful when you need to compare a live page against a reference design, inspect dialog-based modals without the overlay being hidden underneath, adjust CSS in the browser, and pass the resulting changes to an AI agent or source-code update workflow.
Install
Install it from the Chrome Web Store:
What it does
| Feature | Role |
|---|---|
| Reference image overlay | Load a design image over the current page |
dialog modal support | Keep the overlay visible when checking modal UI built with dialog |
| Position, opacity, and scale controls | Align the overlay with the live implementation |
| Guides | Add vertical and horizontal guides for pixel-level checks |
| Color diff view | Check color differences between the reference image and the live page |
| Desktop/mobile states | Keep separate overlay states for different viewport widths |
| Configurable breakpoints | Change the breakpoint used to separate desktop and mobile states |
| CSS diff capture | Record browser-side CSS changes after visual adjustment |
| Prompt export | Copy the CSS diff as AI-ready fix instructions |
| Prompt customization | Customize the exported fix prompt for your team or AI agent workflow |
Configuration
The extension supports settings for the review workflow.
- Change the breakpoint used for desktop/mobile overlay states.
- Customize the prompt used when exporting CSS diff fix instructions.
Typical workflow
- Open the page you want to review.
- Load a reference design image.
- Align the overlay using position, opacity, scale, and guides.
- Set a CSS baseline, make visual adjustments in the browser, and capture the diff.
- Copy the exported prompt and use it with an AI agent or source-code update workflow.
Relationship to SpiraCSS
PixelPerfect CSS Diff is not required to use SpiraCSS.
SpiraCSS keeps CSS architecture consistent through structure and Stylelint. PixelPerfect CSS Diff covers a different part of the workflow: checking the visual result against a reference and turning browser-observed CSS adjustments into fix instructions.