Explain whether Dart works in a single-threaded mode?

Dart by default operates in a single-threaded mode, using an event loop model similar to JavaScript. This means that all code runs in one thread, and asynchronous operations do not block the main thread.

For executing parallel tasks, Dart uses Isolates — separate isolated threads with their own memory and event loop. They do not share state directly but communicate via messages.

Example of creating an Isolate:

import 'dart:isolate';

void sayHello(String message) {
  print('Hello from isolate: $message');
}

void main() {
  Isolate.spawn(sayHello, 'Dart');
  print('Hello from main isolate');
}

Thus, the main Dart code is single-threaded, but for parallelism, Isolates can be used.