How to write and run code
Write HTML, CSS, JavaScript, or Python online in 4 steps
Full Documentation DocsWrite code
Syntax highlighting for 10 languages with autocomplete
Organize
Create folders, manage multiple projects
Preview & Debug
Live preview with built-in console
Auto-save & Export
Everything persists, export as ZIP anytime
Why choose this Code editor?
Browser-based IDE with live preview, console, auto-save, and 10 languages
Auto-save system
Everything saves automatically to your browser. Projects, settings, layout, panel sizes - pick up exactly where you left off.
Multi-project support
Create and switch between multiple projects instantly. Each project maintains its own files, folders, and structure.
Folder & file system
Organize code with nested folders. Drag & drop tabs, floating file browser, and full project structure - like a real IDE.
3 Layout modes
Split, Stacked, or Multi-column. Drag panels to rearrange - CSS left, preview center, JS right. Perfect for large monitors. Your layout is auto-saved.
Live preview and console
See HTML/CSS/JS results instantly. Built-in console captures logs, errors, and warnings. Debug without leaving the editor.
Themes and editor settings
Dark and light themes, font size, tab width, word wrap, line highlighting, auto-close brackets. All settings persist between sessions via IndexedDB.
Frequently Asked Questions
Everything you need to know about this Code Editor
How does the auto-save system work?
Everything saves automatically to your browser's IndexedDB storage. Your projects, files, folders, layout preferences, panel sizes, theme, and all settings persist between sessions. Just close and reopen - everything will be exactly as you left it.
Can I work on multiple projects?
Yes! Click the Projects button in the toolbar to create, switch between, rename, or delete projects. Each project maintains its own files, folder structure, and content independently.
How do I organize files in folders?
Click the Folders & Files button to open the file browser. Create nested folders, rename or delete files, and organize your project structure. You can also pin the file browser as a floating, draggable window.
What layout options are available?
Three layouts: Split, Stacked, and Multi-column. You can drag & drop panels to rearrange them however you want - ideal for large monitors where you might want CSS on the left, preview in the center, and JavaScript on the right. All panels are resizable and your custom arrangement is saved automatically.
What programming languages are supported?
This editor supports 11 file types: HTML, CSS, JavaScript, JSON, XML, Python, Java, C, C++, PHP, and plain text. Each language has syntax highlighting powered by CodeMirror, and web languages (HTML, CSS, JS) support autocomplete with Ctrl+Space.
Is my code private and secure?
Your code never leaves your browser. Everything runs locally with zero server communication. Export as ZIP anytime for backup or sharing.
How to write and run HTML CSS JavaScript online?
Open the editor, write HTML in the first tab, CSS in the second, and JavaScript in the third. The live preview panel shows your result instantly. Use the built-in console to debug JavaScript errors and log output.
Is this a free alternative to CodePen?
Yes. This code editor offers live preview, multi-file editing, and a built-in console like CodePen, but runs entirely in your browser with no account required. Projects auto-save to IndexedDB and you can export everything as a ZIP file.
Technical Details
How this browser-based code editor works under the hood
Syntax Highlighting Engine
This code editor online uses CodeMirror 5 for syntax highlighting across 10 languages: HTML, CSS, JavaScript, JSON, XML, Python, Java, C, C++, and PHP. Six dedicated mode parsers (htmlmixed, css, javascript, xml, python, clike) handle tokenization. The parser runs incrementally - only re-highlighting changed regions for fast update performance even on large files.
Auto-save & Persistence
The web code editor auto-saves every change to IndexedDB with per-file storage and folder structure preservation. Each file maintains independent undo history and cursor position. Data persists across browser sessions with zero server dependency - your code never leaves the browser. Recovery from accidental tab closure is automatic.
Editor Features
Built-in features include line numbers, auto-indentation, bracket matching and auto-closing, search and replace with regex support, code folding, and configurable tab width (2/4/8 spaces). The online code editor supports dark and light themes, adjustable font sizes, word wrap toggle, and active line highlighting - all settings persist between sessions.
File Management System
Manage multiple files and folders with drag-and-drop organization, rename, and delete operations. Import files from your local system or export the entire workspace as a ZIP archive. The code editor supports simultaneous editing of multiple files with instant tab switching and maintains a complete virtual filesystem in IndexedDB storage.
Live Preview and Console
The live preview panel renders HTML, CSS, and JavaScript output in a sandboxed iframe with automatic resource resolution. The built-in console captures console.log(), errors, and warnings from the preview, and supports direct JavaScript execution via the command input. Preview updates on every keystroke.
Layout System and Projects
Three layout modes (split, stacked, multi-column) with draggable, resizable panels. Each project maintains an independent virtual filesystem in IndexedDB with nested folders, file metadata, and undo history. Switch between projects instantly without losing state. Export any project as a ZIP archive.