Tessera

Tessera is a responsive design testing tool that lets developers view their web applications across multiple device breakpoints simultaneously in a single synchronized mosaic. Instead of the traditional workflow of resizing and checking individual breakpoints in DevTools, Tessera displays phones, tablets, laptops, and desktops all at once with real viewports and accurate device pixel ratios.

Key features include live synced scrolling across all viewport tiles, real Playwright sessions for true interaction and isolation, DPR-accurate screenshot captures for PR evidence, and shareable read-only mosaic links for team reviews. Developers can inspect overflow issues, test responsive layouts, and validate designs without the repetitive resize-check loop.

Tessera is designed for web developers and QA teams who need efficient responsive testing workflows. It offers a free tier for canvas testing, with Pro features including localhost tunneling via tessera dev, structured overflow findings through tessera check CLI, and the ability to run automated checks in CI/CD pipelines.