A CSS validator checks stylesheets for invalid syntax, malformed values, and broken at-rules so you can fix problems before they reach users. It helps catch missing semicolons, stray braces, typos in property names, and values that browsers ignore. SWEDevTools: Prism runs locally in your browser (no upload), making it safe for proprietary design systems and production CSS snippets.
No. Stylelint enforces conventions and team rules. This validator focuses on correctness: whether the CSS is valid and parsable.
Fix the first reported structural error and re-run. Later errors are often downstream noise from a single missing brace or semicolon.
Yes. Copy only the CSS content (string/template literal contents) and validate that snippet.
Validation checks syntax/correctness, not browser support. Use compatibility tooling separately.
No. Use Prettier for formatting and a minifier for minification.
Generally yes. If a prefixed property is flagged, double-check spelling and value syntax.
Yes. For debugging, start with the smallest snippet that reproduces the issue, then validate the full file.
Common causes are invalid values (wrong keyword), missing semicolons, or a mismatched brace earlier in the file.
smalldev.tools is no longer available. Prism by SWEDevTools offers the same developer tools and more, with offline support, pipeline chaining, and completely free usage — no signup required.
Yes. Prism formats and validates CSS entirely in your browser — no uploads, no tracking, and full offline support. Chain CSS tools with other Prism utilities in pipelines.