A software development kit (SDK or "devkit") is typically a set of development tools that allows a software engineer to create applications for a certain software package, software framework, hardware platform, computer system, video game console, operating system, or similar.

It may be something as simple as an application programming interface in the form of some files to interface to a particular programming language or include sophisticated hardware to communicate with a certain embedded system. Common tools include debugging aids and other utilities often presented in an IDE. SDKs also frequently include sample code and supporting technical notes or other supporting documentation to help clarify points from the primary reference material.

A software engineer typically receives the SDK from the target system developer. Often the SDK can be downloaded directly via the Internet. Many SDKs are provided for free to encourage developers to use the system or language.

Typically, an SDK includes a visual screen builder, an editor, a compiler, a linker, and sometimes other facilities. The term is used by Microsoft, Sun Microsystems, and a number of other companies.

A Software Development Tools is a program or application that software developers use to create, debug, or maintain other programs and applications. The term usually refers to relatively simple programs that can be combined together to accomplish a task, much as one might use multiple hand tools to fix a physical object.

The history of software tools began with the first computers in the early 1950s that used linkers, loaders, and control programs. Tools became famous with Unix in the early 1970s with tools like grep, awk and make that were meant to be combined flexibly with pipes.

Tools were originally simple and light weight. As some tools have been maintained, they have been integrated into more powerful integrated development environments (IDEs). These environments consolidate functionality into one place, sometimes increasing simplicity and productivity, other times sacrificing flexibility and extensibility. The workflow of IDEs is routinely contrasted with alternative approaches, such as the use of Unix shell tools with text editors like Vim and Emacs.

The distinction between tools and applications is murky. For example, developers use simple databases (such as a file containing list of important values) all the time as tools. However a full-blown database is usually thought of as an application in its own right.

For many years, computer-assisted software engineering (CASE) tools were sought after. Successful tools have proven elusive. In one sense, CASE tools emphasized design and architecture support, such as for UML. But the most successful of these tools are IDEs. The ability to use a variety of tools productively is one hallmark of a skilled software engineer.