How do I encode a Dart string in base64? [duplicate]

There is no need to use the crypto package since the core libraries provide built-in support for base64 encoding and decoding.

https://api.dartlang.org/stable/2.1.0/dart-convert/dart-convert-library.html

import 'dart:convert';

main() {
  final str = "Hello world";
  final bytes = utf8.encode(str);
  final base64Str = base64.encode(bytes);
  print(base64Str);
}