Test and preview HTML code.

Checking whether a snippet renders usually means saving a file, switching to a browser, and reloading after every edit. The tester above removes that loop. Type or paste markup on the left and the panel on the right redraws as you type, with your CSS applied and your scripts running the way they will on a real page. Nothing is uploaded and nothing is logged, so the markup stays on your machine.

The preview runs inside a sandboxed frame on its own origin, so test code can do as it likes without touching the page around it. The frame is allowed to run scripts and nothing else, which means a pasted script executes and paints while alert() stays suppressed and a redirect cannot move the page underneath it. That makes this a reasonable place to look at a snippet someone sent you before you trust it anywhere that matters.

A tester tells you the markup works. It still needs somewhere to live after that, and you can publish an HTML page to get a URL worth sending. If the snippet came out of an AI tool rather than your editor, you can put a Claude output online once it looks right in the preview.

The tester is free and needs no signup, like the rest of NudgeHost's free developer tools. Hosting is the paid side of the site rather than the tools, and you can start for free when a page you have tested needs a link.