🧑💻 Online HTML Editor
Write HTML, CSS and JavaScript with a live preview and console in an isolated sandbox. Templates, autosave in your browser, and .html download.
Saved automatically in this browser. Tab inserts two spaces.
What Online HTML Editor Does
This online HTML editor lets you write HTML, CSS and JavaScript and see the result instantly in a live preview. Output from console.log, warnings and errors appears in a console panel under the preview, so you can debug without opening developer tools — handy on a Chromebook, a school computer or a tablet.
The preview runs in a sandboxed frame with its own isolated origin, so your code cannot touch this site, your cookies or other tabs. Your work is saved automatically in your browser, and one click downloads everything as a single .html file that opens in any browser. Templates give you a starter page, a responsive flexbox layout and a form with validation to build on.
How to Use Online HTML Editor
- Pick a template or start with the starter page
- Edit the HTML, CSS and JS tabs
- Watch the live preview and the console output
- Press Run again to restart scripts from scratch
- Download the result as a single .html file
What Goes Where
| Tab | Put here | Example |
|---|---|---|
| HTML | Page content and structure | <h1>, <p>, <button>, <form> |
| CSS | Styles — colors, layout, fonts | body { font-family: system-ui; } |
| JS | Behavior — runs after the page loads | document.querySelector('button') |
What Code in the Preview Can Do
| Allowed | Blocked |
|---|---|
| Run JavaScript and change the page | Reading this site’s cookies or storage |
| alert(), confirm() and prompt() dialogs | Opening pop-up windows or new tabs |
| Form submit events and validation | Navigating the page around the preview |
| CSS animations, canvas and SVG | localStorage and sessionStorage in your code |
How to Read Your Result
Learning with the console
When something does not work, look at the console first. Errors include a line number, and adding console.log(value) at key points shows what your code is actually doing. Change one thing at a time so you know which change fixed — or broke — the page.
Why the JavaScript runs last
Your JavaScript is placed after the HTML, at the end of the body, so every element already exists when the script runs and document.getElementById finds it. This is the same reason many real pages load scripts at the bottom or with the defer attribute.
From editor to website
The downloaded .html file is a complete page with the CSS and JavaScript inside it. For a real site, you would normally split them into separate .css and .js files and link them, which makes the code easier to reuse and cache.
Limitations & Accuracy Notes
- The sandbox blocks access to localStorage, cookies and pop-ups inside the preview.
- One HTML, one CSS and one JavaScript file per project; there is no package manager or build step.
- Autosave keeps one project per browser; download to keep versions.