# Diffraction

> UI review for GitHub pull requests. Find visual and interaction regressions across browsers and screen sizes, with recorded evidence for every finding.

Diffraction reviews changed web applications from GitHub pull requests. Findings are called aberrations and link to recorded browser evidence. A replay is historical evidence, not a live application. Coverage is limited to the flows, browsers and viewports actually executed.

## UI review

- [Photon Engine](https://www.diffraction.sh/photon-engine): How Diffraction reviews changed applications, from context and exploration to findings and evidence.
- [Photon Engine overview](https://www.diffraction.sh/text/photon-engine.md): Public review principles and frequently asked questions.

## For your role

- [UI review for your role](https://www.diffraction.sh/for): UI review framed for executives, designers and QA, engineers, and engineering leads. Product experience review for UI-affecting GitHub PRs on web apps. hello@diffraction.sh.
- [UI review for executives](https://www.diffraction.sh/for/executives): Product experience review for UI-affecting GitHub PRs. Catch costly aberrations before they hit brand, conversion, or governance. Design-partner interest: hello@diffraction.sh.
- [UI review for designers and QA](https://www.diffraction.sh/for/designers-and-qa): Verify the shipped UI matches intent on UI-affecting GitHub PRs. Evidence you can replay, not screenshot arguments alone. hello@diffraction.sh.
- [UI review for engineers](https://www.diffraction.sh/for/engineers): See what the running PR head actually does before you merge UI-affecting changes. Overview for agent and human PRs on web apps. hello@diffraction.sh.
- [UI review for engineering leads](https://www.diffraction.sh/for/engineering-leads): Confidence and efficiency at the PR boundary. Fewer post-merge product surprises without turning every PR into a manual QA session. hello@diffraction.sh.

## MCP and CLI

- [Install Diffraction MCP and CLI](https://www.diffraction.sh/developers): Setup for Claude Code, Cursor, Codex and other clients.
- [Agent installation and usage guide](https://www.diffraction.sh/text/developers.md): Commands, tools, permissions and evidence workflow.

## Documentation

- [Documentation](https://docs.diffraction.sh): The authoritative Mintlify documentation.
- [Review workflow](https://docs.diffraction.sh/docs/site/lifecycle): Planning, execution and review lifecycle.
- [Reading evidence](https://docs.diffraction.sh/docs/site/reviews): Findings, recordings and coverage limits.
- [Documentation agent index](https://docs.diffraction.sh/llms.txt): Current documentation pages in Markdown.
- [Full documentation](https://docs.diffraction.sh/llms-full.txt): Complete documentation text.

## Blog

- [The Three Checkboxes That Moved Almost a Billion Dollars](https://www.diffraction.sh/text/blog-three-checkboxes-almost-billion-dollars.md): On 11 August 2020, Citibank meant to send $7.8 million in interest. A silent default in Oracle Flexcube sent nearly $894 million instead, and three people signed off.
- [Six People and a National Signup Flow](https://www.diffraction.sh/text/blog-six-people-national-signup-flow.md): HealthCare.gov launched on 1 October 2013. By the morning of 2 October, war-room notes recorded six successful enrolments.
- [The Button That Was Costing $300 Million a Year](https://www.diffraction.sh/text/blog-button-costing-300-million-a-year.md): Jared Spool's classic case study: a major $25B retailer's checkout forced Login or Register. The flow worked, and still cost hundreds of millions until someone watched real behaviour.
- [A code diff is only part of the picture.](https://www.diffraction.sh/text/blog-why-ui-changes-need-ui-review.md): Why we’re building a review layer for the experience on the other side of a pull request.

## Optional

- [Full public content](https://www.diffraction.sh/llms-full.txt): Product overview, questions and editorial content.
- [Website](https://www.diffraction.sh/): Product overview and interactive example.
- [Sitemap](https://www.diffraction.sh/sitemap.xml): Canonical public pages.
- [RSS feed](https://www.diffraction.sh/feed.xml): Blog updates.