Free Online HTML Editor

HTML Viewer Cat gives you a fast, distraction-free HTML editor that runs entirely in your browser. Write or paste HTML on the left, see the result on the right — updated in real time with every keystroke. No account, no downloads, no configuration.

What makes a good online HTML editor?

A good HTML editor needs three things: fast feedback, clean syntax highlighting, and no friction. You should be able to open a tab and start coding immediately. That's what HTML Viewer Cat is built for — whether you're debugging a layout, learning HTML for the first time, or prototyping a component.

Features

• Live preview — see rendered HTML as you type, with zero delay
• Syntax highlighting — color-coded tags, attributes, and values powered by CodeMirror
• Responsive testing — switch between phone, tablet, and desktop previews
• Draggable panes — resize the editor and preview panels to your preference
• Fullscreen preview — expand the preview to see your HTML at full scale
• Mobile support — works on phones and tablets with a toggle between editor and preview

Who is this for?

Anyone who works with HTML. Front-end developers testing snippets, students learning web development, email marketers previewing templates, and anyone who needs a quick scratchpad for HTML. Because it runs in the browser with no server-side processing, your code stays private and loads instantly.

How to use the editor

1. Open the editor
2. Type or paste your HTML into the left panel
3. Watch the preview update in real time on the right
4. Use the device icons to test responsive layouts
5. Drag the divider to resize the panels