Dart Lesson 86 of 102 3 min read

Using Packages from pub.dev in Dart

Learn to find, add, use and update Dart packages from pub.dev: pubspec.yaml, dart pub add, version constraints and pubspec.lock.

A package is a bundle of Dart code that someone has published for others to use. pub.dev is the official home of Dart and Flutter packages, with tens of thousands available for HTTP, databases, dates, state management, testing and much more.

pubspec.yaml #

Every Dart project has a pubspec.yaml at its root. It names the project and lists what it depends on.

name: my_app
description: A sample command-line application.
version: 1.0.0

environment:
  sdk: ^3.5.0

dependencies:
  http: ^1.2.0
  path: ^1.9.0

dev_dependencies:
  lints: ^5.0.0
  test: ^1.25.0

YAML uses indentation for structure. Use two spaces, never tabs.

Adding a package #

Let the tool edit the file and download the code:

dart pub add http
dart pub add --dev test

In a Flutter project the command is flutter pub add http.

If you edit pubspec.yaml by hand, fetch the packages afterwards:

dart pub get

Using it #

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

Future<void> main() async {
  final url = Uri.parse('https://jsonplaceholder.typicode.com/todos/1');
  final response = await http.get(url);

  print(response.statusCode);
  print(response.body);
}

The import path is package:<package name>/<file>.dart. The package’s page on pub.dev shows the exact line.

Version numbers and constraints #

Packages use semantic versioning: MAJOR.MINOR.PATCH.

• PATCH (1.2.3 to 1.2.4): bug fixes.
• MINOR (1.2.3 to 1.3.0): new features, still compatible.
• MAJOR (1.2.3 to 2.0.0): changes that may break your code.

The caret form (^) is the standard choice: take improvements automatically, but not breaking changes.

pubspec.lock #

After resolving versions, pub writes the exact version of every package to pubspec.lock. Everyone who then runs dart pub get gets the same versions, so the code behaves the same on every machine.

• For an app, commit pubspec.lock to version control.
• For a package you publish, it matters less, since users resolve their own versions.

Keeping packages up to date #

dart pub outdated          # what could be upgraded
dart pub upgrade           # newest versions allowed by your constraints
dart pub upgrade --major-versions   # also move to new major versions
dart pub remove http       # drop a package
dart pub deps              # show the dependency tree

Choosing a good package #

Anyone can publish to pub.dev, so look before you depend on something.

Each dependency is code you must keep updated and trust. For a ten-line helper, writing it yourself is often better.

Packages worth knowing #

Other dependency sources #

dependencies:
  # A folder on your machine, useful while developing two packages together
  my_utils:
    path: ../my_utils

  # Straight from a Git repository
  some_fork:
    git:
      url: https://github.com/someone/some_fork.git
      ref: main

Try it yourself #

Create a project, add the intl package, and print today’s date formatted as 10 October 2026. Then run dart pub outdated and dart pub deps and read what they report.