Happo

Happo is a visual regression testing service that catches UI changes on every pull request, from a button that moved to a contrast that dropped or an animation that changed.

Screenshots of components and pages are rendered in Chrome, Firefox, Safari and Edge, on iPhone and iPad, and in native iOS and Android apps, then compared with the baseline of the main branch. Differences are shown on a comparison page where reviewers approve or reject them, and render errors block the approval. Happo integrates with component libraries and end-to-end test frameworks such as Storybook, Playwright and Cypress, and reports its status on the pull request.

Happo is a commercial service with a free plan of 5,000 snapshots a month.