Welcome to HCODX Online Compiler
Quick Start:
Ctrl+Enter Run code
Ctrl+S Save / Download
Ctrl+L Clear output
Select a language and start coding.
Compile and run Dart code online instantly with HCODX. Our free cloud-based Dart compiler supports real-time execution, standard input, syntax highlighting, and code download. No installation or configuration required. Start coding in Dart now.
Run Dart instantly without installing any IDEs or configuring environments. Our cloud-based Dart handles libraries, runtimes, and dependencies automatically so you can focus on writing code.
Whether you are studying algorithms in Dart, practicing data structures in Dart, or exploring functional programming, our tool provides real-time stdout/stderr feedback with interactive standard input support.
HCODX is a free online compiler and code runner: write code in your browser, execute it on a cloud sandbox, and interact with your program through a live terminal. Students use it for coursework and interview practice; developers use it to test snippets in 85+ languages without setting up a local environment.
Dart exists today for one dominant reason: Flutter, Google's UI toolkit that compiles a single codebase to iOS, Android, web, and desktop, powering apps from BMW, eBay Motors, and Google Pay. But the language stands on its own — Dart 3 brought sound null safety everywhere, records, and pattern matching, and the VM offers both JIT for fast iteration and AOT for production. Before logic gets buried inside a widget tree, it pays to prove it in plain Dart, and that's what this page is for: your program runs on the Dart VM with a live terminal, so stdin.readLineSync() pauses mid-run for your real input.
import 'dart:io';
void main() {
stdout.write('Enter your name: ');
final name = stdin.readLineSync() ?? 'friend';
stdout.write('How many squares should I compute? ');
final n = int.parse(stdin.readLineSync() ?? '0');
final squares = [for (var i = 1; i <= n; i++) i * i];
print('Hi $name! The first $n squares:');
print(squares.join(', '));
print('Their sum is ${squares.fold<int>(0, (a, b) => a + b)}.');
}Extract the model classes, parsing routines, and state logic from a Flutter feature and verify them as pure Dart before a single widget rebuild — a habit that saves hours of hot-reload guessing. Bootcamp and university students starting Flutter tracks can master the language layer (null safety, futures, collections, cascade notation) here first, and mobile-developer interview prep often includes plain-Dart algorithm rounds that map directly onto this stdin-driven format. Collection-if, spreads, and records all behave exactly as they will in your app. HCODX is a free online Dart editor, runner and interpreter — an IDE-grade compiler and playground to write and run code online, execute code with live output and live preview, no downloads or web server required.
Yes — the Dart VM process is attached to a live terminal, so readLineSync() blocks until you type a line and press Enter. Pair it with stdout.write for same-line prompts (print adds a newline), and you get the standard interactive console pattern shown in the example above.
No — Flutter needs its rendering engine and a device or emulator target, which a console sandbox doesn't provide. What runs here is command-line Dart on the VM, which is ideal for the non-UI majority of your code: models, validation, algorithms, async logic with Future and Stream.
Sound null safety is on — Dart 3 requires it — so nullable types must be handled explicitly, as the ?? defaults in the example show. Packages from pub.dev can't be fetched in the sandbox; you're working with the core libraries (dart:core, dart:io, dart:convert, dart:math, dart:async), which cover most practice needs.
Your current code will be replaced with the default sample. This cannot be undone — download your code first if you want to keep it.
You have unsaved changes. Do you want to save your code before continuing?