Software development kits (SDKs) and application programming interfaces (APIs) are two different types of tools that developers can use to build their products. They serve different roles in providing the frameworks and operations that drive functionality in computer programs and online services.
What is a software development kit (SDK)?
Software development kits (SDKs) are comprehensive collections of tools that help developers program within specific ecosystems. SDKs are often provided by parties like mobile platforms (iOS, Android), gaming environments (Unity), and cloud computing platforms (Amazon Web Services, Google Cloud) to for programmers to build using their products.
SDKs typically include a suite of tools that span a broad range of functionality. Usually, this is tailored to the purpose of the platform providing the SDK. For instance, a mobile phone SDK may provide a programming code editor, debugging software, and libraries of pre-packaged code that account for basic functions like statistical calculations, 3D rendering, and integrating with location services—so they don’t have to be written from scratch. An SDK may also provide ways for applications to communicate externally with other software, called application programming interfaces (APIs). More information about APIs can be found below.
In this way, SDKs can be considered as a type of “outline” that makes it easier to write the “essays” that become computer programs. They provide concepts, organization, and snippets of text from which developers can build out their own projects with minimal friction.
In crypto, SDKs are found in multiple forms. Perhaps the most high-profile SDKs are the ones associated with specific blockchain products. The Cosmos SDK is a good example: it provides the tools necessary for developers to create purpose-built blockchains connected to the Cosmos Hub. Whereas building a blockchain application may be a daunting task without an adequate starting point, the Cosmos SDK provides every basic tool necessary to connect to the Hub—including other Cosmos-connected chains—and construct almost any desired functionality.
What is an application programming interface (API)?
Application programming interfaces (APIs) are also tools used in software development. Their primary role is governing how different software systems “speak” to each other. APIs may exist independently of SDKs, but SDKs often include one or more APIs because external communication is often desirable—and even required—in the increasingly interconnected world. In this way, the role of APIs is more limited in its scope than the role of SDKs, but that doesn’t mean that they are any less important. In fact, most people using the internet interact (indirectly) with multiple APIs every day.
At a most basic level, APIs connect two or more pieces of software. More specifically, they define a set of rules that allow for *certain types *of information to pass between programs. This optimizes security while still allowing for the exchange of necessary data. APIs work based on “call and response,” where one program requests certain data from another, and the other responds by sending it (if the prerequisites are met).
Take the example of chart-making software that helps users visualize financial asset prices. The information for the pricing of various financial assets (*e.g., *stocks, cryptocurrencies) must come from a primary source like brokers or exchanges. These data providers allow information sharing through APIs that the chart-making software requests, in order to make it available to its users.
In crypto, APIs are used for a multitude of purposes. Centralized exchanges (like Bitstamp) provide APIs for pricing data (as above) and to facilitate trading workflows, and this data is sometimes also available through third parties like CoinGecko and CoinMarketCap. Blockchain explorers like Etherscan ( thereum) and Solscan ( olana) also offer APIs for developers building applications dependent on data about transactions on their respective chains.
Comparison of SDKs and APIs
Both SDKs and APIs are used to build software products with important functionality. However, they serve slightly different functions. Whereas APIs are more focused instruments that facilitate communication of data between pieces of software, SDKs are more wide-reaching in their support for multiple aspects of software development. Further, SDKs may contain APIs within their suite of offerings. In other words, an API is like a screwdriver where an SDK is the whole toolbox.
SDKs are generally provided by platforms for developers in a specific ecosystem, and rarely do SDKs effectively span multiple ecosystems. APIs, however, are built so that different systems can connect with each other, so they are more generalizable. Despite their differences, however, both are very important tools for software design and implementation, and their respective functions are highly valued in all technological enterprises.
SDK vs API essentials
Software development kits (SDKs) are toolkits that contain multiple ways for developers to build functionality within an ecosystem like a mobile phone operating system, a game, or a blockchain.
Application programming interfaces (APIs) are more focused tools provided by platforms so that data can be integrated—securely—across different programs.