AnyTool
Your files never leave your device. All processing happens locally in your browser.

How do I edit HTML, CSS, and JavaScript online with live preview?

Type into AnyTool's three CodeMirror panes — HTML, CSS, and JS — and the combined page renders instantly in a sandboxed iframe as you type, with console.log, warnings, and errors captured in a panel below. You can switch layouts, format with Prettier, load examples, and export or share — all in your browser, so your code never leaves your device.

  • Three HTML/CSS/JS CodeMirror panes with instant debounced live preview
  • Captured console output and runtime errors — no devtools needed
  • Layout switch (split, stacked, editor-only, preview-only) and examples library
  • One-click Prettier format, export single-file HTML or ZIP, and share-via-URL
  • 100% client-side — preview runs in a sandboxed iframe, code never leaves your browser, free, no signup

What is

HTML/CSS/JS Live Editor

An HTML/CSS/JS live editor is an online playground with separate HTML, CSS, and JavaScript panes and an instant live preview. AnyTool's renders the combined page in a sandboxed browser iframe — no server — with captured console output, layout presets, Prettier formatting, export, and share-via-URL.

Developer Tools

Related terms

CodePenJSFiddleOnline Code EditorCodeMirrorLive Preview

How to Edit HTML, CSS, and JS with Live Preview

Edit HTML, CSS, and JavaScript in three panes and see an instant live preview entirely in your browser.

15 secWeb browser
  1. 1

    Write code

    Type into the HTML, CSS, and JS CodeMirror panes, or load one of the example templates.

  2. 2

    See it live

    The combined page renders instantly in a sandboxed iframe as you type, with console output captured below.

  3. 3

    Format, export, or share

    Optionally format with Prettier, then export single-file HTML or ZIP, or share via URL.

Result: A live-previewed HTML/CSS/JS page

Frequently Asked Questions

Yes — it is completely free with no signup, no account, and no limits.

The HTML/CSS/JS live editor is 100% free with no account, subscription, or paid tier. You can edit, preview, format, export, and share as much as you want — unlike CodePen or CodeSandbox, which gate private projects and saving behind a paid Pro account.

No — the preview runs in a sandboxed iframe on your device and is never uploaded to any server.

Your HTML, CSS, and JS are assembled and rendered in a sandboxed iframe (allow-scripts only, no same-origin) right on your machine, so the code cannot read the page, cookies, or storage, and it is never sent to a server. Even sharing encodes the state into the URL, so AnyTool both previews and shares with zero backend — it works offline and keeps private code private.

Yes — same three-pane live-preview workflow, but fully client-side with no signup.

It gives you the same CodePen/JSFiddle experience — separate HTML, CSS, and JS panes with an instant live preview and a captured console — but unlike CodePen, JSFiddle, JS Bin, or CodeSandbox it runs and saves nothing on a server, needs no account, and works offline.

Yes — export a single-file HTML or a ZIP, and share via a backend-free URL link.

You can download a standalone index.html with the CSS and JS inlined, or export a ZIP with separate files, all generated in the browser. Sharing compresses the three sources and layout into the URL hash, so a single link reproduces the editor with no server storage.

Detailed Explanation

Methodology

How the HTML/CSS/JS Live Editor Renders the Preview

AnyTool gives you three CodeMirror panes — HTML, CSS, and JavaScript — and assembles them into a single document that is rendered inside a freshly created sandboxed iframe (sandbox="allow-scripts" only, with no same-origin) via srcdoc, so the framed code cannot read the parent page, cookies, or local storage and nothing is fetched from a CDN. The preview updates as you type with a debounced rebuild (~200ms), and a bootstrap injected before your JS overrides console.log/warn/error/info/debug and captures window.onerror and unhandledrejection, posting each entry back via postMessage so a captured console panel streams output and runtime errors live. You can switch layouts (split, stacked, editor-only, preview-only), load example templates, format each pane with bundled Prettier, export a single-file index.html or a ZIP, and share by encoding the sources into the URL hash. Nothing is sent to a server.

  • Three HTML/CSS/JS CodeMirror panes assembled into a sandboxed srcdoc iframe
  • Instant debounced live preview — no Run button needed
  • Captured console output plus window.onerror and unhandledrejection
  • Layout presets, examples library, and one-click Prettier formatting
  • Export single-file HTML or ZIP and share-via-URL with state in the link, no backend
Privacy & Security

Privacy and Offline Use

Editing, preview rendering, console capture, formatting, export, and sharing all happen in the browser with no runtime CDN, so your code never leaves the device — unlike CodePen, JSFiddle, JS Bin, CodeSandbox, StackBlitz, Replit, or PlayCode, which save snippets on a server or run them in a cloud VM, and most of which require an account for private work. The preview runs in a sandboxed allow-scripts iframe with no same-origin access, and sharing encodes the HTML, CSS, JS, and layout into the URL hash, so it needs no backend. It works offline after first load and has no signup or paid tier, making it one of the few three-pane live editors that both previews and shares fully locally while still capturing the console.

HTML/CSS/JS live editor: AnyTool vs typical online editors
CapabilityAnyToolTypical editors
Preview locationIn-browser sandboxed iframeOften server-rendered or cloud VM
Live previewYes (debounced as you type)Often click Run
Captured consoleBuilt inOften missing or devtools-only
Share without backendYes (URL-encoded state)Usually server-side link
Signup / paid tierNoneOften Pro account for private/save

Capabilities reflect the live AnyTool tool; competitor behavior varies by service.