The Rise of REST and Distributed Systems

The concept of an API predates even the advent of personal computing, let alone the Web, by a very long time! The principle of a well-documented set of publicly addressable "entry points" that allow an application to interact with another system has been an essential part of software development since the earliest days of utility data processing. However, the advent of distributed systems, and then the web itself, has seen the importance and utility of these same basic concepts increase dramatically.

-Martin Bartlett

According to, the first web API was introduced by Salesforce on February 7th, 2000. However, that API was not to be made publicly available to the world at the time. Back then, Salesforce launched its web-based sales force automation as an "Internet as a service", and XML APIs became part of from day one. The main role of these APIs was for customers to share data across their different business platforms and applications.

Meanwhile, during the same year, about 9 months later, eBay launched the eBay Application Program Interface (API), along with the eBay Developers Program, making eBay’s APIs openly available for anyone to use. Therefore, both Salesforce and eBay are often regarded as the pioneering companies who introduced the first ever public APIs to the world.

Then on July 16, 2002, Amazon launched Web Services allowing developers to incorporate's content and features into their own web sites. Web Services allowed third party sites to search and display products from in an XML format.

Since then, companies such as Flickr, Facebook, and Twitter followed suit and have all released their own publicly available web APIs.

According to, there are over 25,000 RESTful APIs open to the public. As you can imagine, RESTful Web APIs have become extremely popular and are nowadays the defacto standard for communication across different systems and transportation of data over the web.

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