# Introduction

Welcome to the Yocto Project Software Development Kit (SDK) Developer's Guide. This manual provides information that lets you use both the standard Yocto Project SDK and an extensible SDK to develop applications and images using the Yocto Project.

Prior to the 2.0 Release of the Yocto Project, application development was primarily accomplished through the use of the Application Development Toolkit (ADT) and the availability of stand-alone cross-development toolchains and other tools. With the 2.1 Release of the Yocto Project, application development has transitioned to within a more traditional SDK and extensible SDK.