What is an SDK? SDK vs Library vs Framework

SDKs have become an integral part of the mobile app development process, but what exactly is an SDK and how does it differ from other components like libraries and frameworks? There seems to be no consensus and a lot of confusion about that, so we will try to demystify these terms and take a look at what an SDK is and how it differs from a library or a framework.

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What is a library?

We’ll start with libraries since they have the smallest scope of the three. Simply put, a library is a packaged, reusable chunk of code that performs a certain function or set of closely related functions. You can insert a library into your application and call it when you need to implement that function without having to write the code from scratch.

Suppose that instead of an application, you are building a house. One of the things you will need for that house is a stove, but it will not be very practical for you to build it from scratch when you could just buy one off the shelf. A library is to an application what the stove is to that house.

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What is an SDK?

SDKs have a wider scope than libraries do. In fact, all SDKs will contain one or more libraries. An SDK is a collection of libraries, APIs, documentation, utilities, and/or sample code that help you implement certain features without having to do the work from scratch. SDKs vary in scope and function from implementing a feature or set of features, like an analytics SDK for instance, to building whole applications for a specific platform, as is the case with the Android SDK for example.

Going back to our house analogy, if a library is a stove, then an SDK is a whole kitchen. While you can go and buy all your kitchen appliances, cabinets, and counters separately, it will be a lot easier to buy a full kitchen set, complete with built-in appliances and instructions on how to assemble it. SDKs can be limited in scope such as in the case with one room, but they can also have a bigger scope of a collection of rooms or even the whole house.

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What is a framework?

Frameworks are in many ways the inverse of libraries and SDKs. They too are a collection of libraries, APIs, utilities, and documentation to solve common programming requirements so you don't have to do the work yourself. However, they do that by giving you a foundation on top of which you can build your app rather than giving you the building blocks. While you insert a library into your application and call it from your code to perform certain functions, frameworks require you to insert your code into them and they call your code at the right moment.

In our house analogy, a framework will be exactly that, the house's framework. It is the collection of beams and posts upon which you build your rooms, complete with electrical wiring and plumbing. Having this ready-made structure upon which you can build your house will save you a huge amount of time and effort.

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Conclusion

There are a ton of mobile app development tools out there, but without knowing the difference between them it will be difficult to make the most out of them. Now that you know what exactly an SDK is and how it differs from libraries and frameworks, you can decide on which of these to use and when in order to build a world-class app.