Cross posting an article written by me last year for a technical magazine but was not published.
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Web is growing fast with lots of new services being added everyday. Advancements in technologies like HTML5, JS, and CSS3 make the web so powerful that we can almost do everything on the web today. With the increase in the number of services, the need for cross referencing the services also increases. A web application providing photo editing service may want to use the service of photo sharing sites like Instagram or Flickr. Almost all the service providers expose APIs for others to consume their services. While consuming the service from a web application back-end is easier, it is not so easy using the client side technologies. Browsers impose lots of restrictions in accessing resources originating from domains other than the current domain.
