Figuring out exactly which elements a CSS selector will match — especially with pseudo-classes like :nth-child() or combinators — often means editing your actual stylesheet and reloading a page to check. This tool lets you test a selector against sample (or your own) HTML instantly, with real browser matching.
What Is the CSS Selector Tester?
Enter a CSS selector and see it evaluated live against editable sample HTML, using the browser’s own querySelectorAll() — every matching element is visually highlighted in the rendered preview, and a status line reports the total match count or any selector syntax error.
How to Use It
- Open the tool at /tools/css-selector-tester.
- Edit the sample HTML, or paste in your own markup.
- Type a CSS selector into the input field.
- Check the highlighted matches and the match count.
Key Features
- Real browser selector engine, using
querySelectorAll()directly, so behavior (including modern pseudo-classes) matches your actual browser exactly. - Live syntax error reporting, showing the same
SyntaxErrormessage you’d see debugging in DevTools for an invalid selector. - Editable sample HTML, so you can test selectors against your own project’s markup.
- Visual match highlighting, outlining every matched element directly in the rendered preview.
When to Use This Tool
- Debugging why a CSS rule isn’t applying by confirming whether the selector actually matches the intended elements.
- Learning CSS selector syntax (combinators, pseudo-classes, attribute selectors) with instant visual feedback.
- Testing a selector before using it in JavaScript’s
querySelector/querySelectorAll.
Try It Now
Open CSS Selector Tester directly, or press ⌘K and type the tool name from anywhere on the site.
Part of the CSS Tools collection on WebdevToolbox — free, browser-based developer tools with no login required.