How does asynchronous programming work in Flutter?

Dart executes synchronous code to completion, then drains microtasks, then handles events. A Future represents a value available later. await suspends the current async function and lets the event loop run other work. It does not create a thread, so a long synchronous loop still blocks rendering.

Future<DashboardData> loadDashboard(ApiClient api) async {
  final statsFuture = api.fetchStats();
  final activityFuture = api.fetchActivity();

  try {
    final stats = await statsFuture;
    final activity = await activityFuture;
    return DashboardData(stats: stats, activity: activity);
  } on TimeoutException {
    throw DashboardException('Request timed out');
  }
}

• Never perform network or CPU work directly in build
• Handle errors with try and catch; unhandled async errors surface as zone errors
• Use Future.wait for a fixed group of futures and decide on eagerError behaviour
• Cancel or ignore stale responses when a newer request supersedes them
• Use unawaited only when intentionally fire-and-forget, and still handle failures

What await does not do

await does not run work in parallel on another thread. Two futures can progress concurrently because the underlying I/O is asynchronous, but Dart code still runs on the isolate's event loop. Parsing a large JSON payload or compressing an image synchronously will jank even inside an async function.