> For the complete documentation index, see [llms.txt](https://docs.atsign.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.atsign.com/dart-sdk/getting-started/overview.md).

# Overview

Overview of the Dart SDK

Atsign's SDK written in Dart is the most mature SDK out of all SDKs offered by the platform. [AtClient 3.x](https://pub.dev/packages/at_client/versions) currently contains the most amount of features and we try our best to uphold backwards compatibility with clients that have existed since 2018.

The Dart SDK is a client-side SDK that allows developers to interact with their atServer and ultimately create secure end-to-end encrypted and identity-backed data exchanges with other Atsigns.

| Where to go next                                            | Why                                                                                                               |
| ----------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------- |
| [Prerequisites](/dart-sdk/getting-started/prerequisites.md) | First, fulfill the prerequisites so that you can start writing programs in the Dart SDK.                          |
| [Quickstart](/dart-sdk/getting-started/quickstart.md)       | Run a simple program that will onboard and write data to your atServer.                                           |
| [Our packages](/dart-sdk/getting-started/our-packages.md)   | Get an overview of the packages we host on pub.dev and which packages you will be using in your Dart applications |

## Flutter Applications

Note that the Dart SDK and Flutter SDK section have lots of overlap. You will be writing code that is referenced in both the [Dart SDK](/dart-sdk/getting-started.md) section and the [Flutter SDK](/flutter-sdk/getting-started.md) section. Dart code such as [AtCollections](/dart-sdk/atcollections.md) and [Events](/dart-sdk/events.md) remain the same in both a Dart and Flutter app. However, subtle things like Keychain Management and Onboarding will be different in the [Flutter SDK](/flutter-sdk/getting-started.md). See [Flutter SDK](/flutter-sdk/getting-started.md) to learn more.