Paste CSS, choose browser targets and compare grid, add and remove modes before changing a build pipeline. The preview runs locally in a worker with project config lookup blocked.
Autoprefixer translates Browserslist targets into CSS prefixes and cleanup decisions. This playground makes that output visible for flexbox, grid, appearance, user-select and other common declarations.
The route uses bundled Autoprefixer and PostCSS in a browser worker. It does not read .browserslistrc, package.json, source maps, environment variables or browserslist-config packages.
Start from a preset, edit CSS and run a controlled preview. Autoprefixer control comments are blocked so the UI options stay authoritative.
Shows the cost and caveats of enabling legacy grid prefixes.
Run the preview to see output CSS, diagnostics and a copyable PostCSS config.
The same CSS can produce different prefixes when Browserslist targets change. Treat the preview as review evidence, then confirm the real repository build.
Grid template prefixes can help legacy review, but autoplace is not a full IE layout guarantee. Keep the caveat visible in pull requests.
A public playground should not resolve packages, read project files, load previous source maps or obey user-provided Autoprefixer control comments.
Use these when CSS prefix output depends on browser targets, build configuration or JavaScript transforms.