What is an API?

The acronym ‘API’ stands for an extremely important part of the world of software development, despite the complete lack of recognition from the wider world.

These three letters stand for Application Programming Interface and without APIs, a whole range of integrated digital services would be unavailable – from posting pictures on social networking sites to sending email via SMS. API implementation is what lets applications, libraries and operating systems understand one another and interact, turning technology and software from complex niche devices to broadly accessible, multi-purpose consumer services.

An API works in a similar way to a user interface; providing an abstract interface for functional interaction between different componenets of different software systems. There are several different categories of API, tailored to specific or general uses. The two main categories are:

• General APIs – this is the most extensive form of API, effectively the part of a programming language that allows for functional interactivity between different programmes. Examples include the Standard Template Library in C++ or the Java API.

• Specific APIs – these are APIs designed for a specific problem or purpose. Examples include Google Maps API, which lets developers access the Google Maps data templates to build visualisations and tools such as journey planners or online pedometres, or an SMS API for text message marketing campaigns.

The most common type of google search volume api though has to be those aimed at web development. Tools for web development are often published freely (though retaining proprietary rights to the code), with the overall intent of facilitating the consturction of an open architecture for web content and data between different applications and online communities.

Web APIs are typically a defined set of HyperText Transfer Protocol request messages, coupled with a definition of the structure for response messages. Often coded in Extensible Markup Language (XML) or JavaScript Object Notation (JSON) format, they allow the combination of multiple services into new online applications commonly known as ‘mash-ups’.

The ability to openly use Web APIs has allowed the creation of a variety of now commonly used web services. Perhaps the best example is the ability to embed content from one web page onto another web page through relatively simple HTML code – for example, posting a YouTube video on a web page rather than simply posting a link to YouTube. Similarly, an API lies behind the ability to upload a video on Flickr and post it on Facebook or MySpace, as well as the ability to stream live feeds from social media networks such as Twitter on other sites.