Online Dart, JavaScript & TypeScript Compiler

DataFormatter includes a full online Dart compiler. When you select Dart and click Run, the page boots the DartPad DDC (Dart Development Compiler) engine — a WebAssembly build of the Dart compiler and runtime that runs entirely in your browser. There is no remote server involved: the Dart SDK, compiler and execution sandbox are all loaded into your browser tab.

The first Dart run loads the WebAssembly engine in the background (a single fetch that takes a few seconds on a typical connection). Subsequent runs are instant because the compiler keeps a persistent incremental compilation session between runs — edit your code, press Run again, and changes compile and execute immediately.

The Dart tab loads by default. Write a void main() function with print() statements, press Run, and the output appears in the panel on the right. The editor includes syntax highlighting; press ⌘/Ctrl + Enter to run from anywhere in the editor.

void main() {
  final name = 'Dart';
  print('Hello from $name — running in the browser!');
}

Hello from Dart — running in the browser!

To read lines from the STDIN box (the collapsible input area below the output pane), use the dartpadReadLine JS function exposed through dart:js_interop — see the "stdin echo" example in the Examples menu for a working template.

• Dart programs execute in a browser sandbox — there is no filesystem, network (fetch) or OS access.
• JavaScript and TypeScript have a 10-second execution timeout; long-running programs are stopped.
• TypeScript is transpiled type-check-free — types exist for editor clarity but are not enforced at compile time.
• The Dart engine loads a WebAssembly bundle on first run (~8 MB); the first run takes a few seconds on slower connections.
• Standard input is available but read via the JS bridge — there is no real terminal or TTY.

Many online compilers send your code to a remote server to run it. This one executes entirely in your browser — Dart through WebAssembly and JavaScript/TypeScript in a sandboxed worker — so there is no code upload, no queue and no server-side logging. That makes it a good fit when you are experimenting with code you would rather keep local.

• ◆Open the Examples menu to load built-in snippets for each language — a quick way to see syntax in action without writing code from scratch.
• ◆Use the collapsible STDIN box to pipe data to your program: for Dart, use the dartpadReadLine JS bridge; for JS/TS, call readLine() which returns the next line or null.
• ◆Dart and JavaScript drafts are separate — switching tabs never loses your code. Each language remembers its last edit.
• ◆Use the Share button to generate a shareable URL containing the current program, ready to send to someone or bookmark.