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In Flutter development it is critical to access APIs that have some kind of authentication and the most popular method is Basic Authentication, which basically consists of sending the user and password in a header.

In Flutter we perform HTTP requests through the native Dart package http/http.dart (https://pub.dev/packages/http).

This package contains a set of high-level functions and classes that make it easy to consume HTTP resources. It is platform independent and can be used on the command line and in the browser.

HTTP request in Flutter

import 'package:http/http.dart' as http;

main() async {

  var response = await http.post(
      'https://api.site.io/new',
      body: {'name': 'doodle', 'color': 'blue'},
  );

  print('Response status: ${response.statusCode}');
  print('Response body: ${response.body}');

}

HTTP Request with Basic Authentication in Flutter

Remembering that Basic Authentication requires that username:password to be Base64 encoded, which in Flutter is done through the Base64Encoder class (https://api.dartlang.org/stable/2.7.0/dart-convert/Base64Encoder-class.html).

In the context of an HTTP transaction, Basic Authentication is a method for an HTTP user agent (for example, Flutter) to provide a username and password when making a request.

Base64Encoder output is sent with the Authorization: Basic header:

Authorization: Basic QWxhZGRpbjpPcGVuU2VzYW1l

Flutter and Dart make it much easier to do this:

import 'dart:convert';
import 'package:http/http.dart';

main() async {

  String username = 'luiz';
  String password = '123';
  String basicAuth = 'Basic ' + base64Encode('$username:$password');

  var response = await http.post(
      'https://api.site.io/new',
      headers: <String, String>{'authorization': basicAuth},
      body: {'name': 'doodle', 'color': 'blue'},
  );

  print('Response status: ${response.statusCode}');
  print('Response body: ${response.body}');

}