Free AI design tells checker for HTML, CSS and Tailwind

Paste the HTML, CSS, Tailwind markup or JSX of a page an AI coding agent built. The checker looks for the default design tells (purple gradients, an Inter-first font stack, a row of identical cards, eyebrow labels, stock marketing phrases and more) and lists each one it finds, with the line, the offending code and what to change. It is a text-pattern check, so it can miss some and flag something you meant; the limits are listed below. It runs in your browser: your code is not sent anywhere.

What it checks

16 rules: 12 design tells and 4 craft checks (visible focus, reduced motion, viewport, image alt text). It reads text patterns, so it cannot judge whether a design is good, and a page can pass and still be bland.

What it can and cannot see

• It reads Tailwind class names written in class="..." or className=... (including strings inside cn() and clsx()), plain CSS and <style> blocks, and oklch() colours. Pasted JSX works.
• It cannot see class names built at run time (such as bg-${colour}-500), custom colours in tailwind.config, styles imported from other files, or a stylesheet you did not paste. It does not run your build.
• The two craft checks for visible focus and reduced motion run on pasted CSS, and on a single HTML page that has its own <style> block or Tailwind classes.
• We have tested it on sample pages we wrote ourselves in the default style (a plain CSS page, a Tailwind landing page and a React component), not on a measured sample of real-world AI-built sites. Treat a clean result as "none of these patterns found".

The same engine is the free, MIT-licensed slop-lint command-line tool, which checks whole folders. The guide to the tells explains each one and the fix, and Looksheet is the set of four finished looks to start from instead.