HATEOAS API

Originally called REST, HATEOAS is a way of designing HTTP APIs as described in Roy Fieldings thesis. The acronym stands for Hypermedia as the Engine of Application State.

It distinguishes itself from other APIs by having the following properties:

• Heavy use of Media Types to allow Backward Compatibility.
• It does not allow clients to construct URLs (unless instructed by the server to do so) to allow for applications to change their URL structure.
• Other than an entry URL and a set of documents describing the Media Types, no additional knowledge should be necessary to use the API.
• Having a nice URL structure is not essential, people in browsers will be clicking on links instead of typing and source code should only contain the root URL.

HATEOAS APIs usually make heavy use of HTTP features like:

• Caching to enable the application to scale better.
• Content Negotiation to support older clients and give users localized versions of resources.
• Conditional PUTs to add Optimistic Concurrency.

Language Support

Some programming languages have ready to use libraries that can help you implement a HATEOAS API:

• Ruby
• NodeJS

Comparison

Method	Browser Accessible	Backward Compatible	Backward Compatible (default)	HTTP Cachable	No URL Construction	URL as Identifier	Stable Pagination	Concurrency Support
HATEOAS	?	Yes	?	Yes	Yes	Yes	?	Yes
media_types-serialization (HATEOAS)	Yes	Yes	Yes	Yes	Yes	Yes	Yes	?
Github (REST)	Yes	Yes	No	No	Yes	Yes	Yes	No
Zalando	No	Yes	Yes	No	No	Yes	Yes	Yes
Facebook Graph API	Yes	Yes	Yes	No	No	No	?	No
Shopify (REST)	Yes	Yes	Yes	No	No	No	Yes	No
GraphQL	No	Yes	No	No	Yes	No	Yes	No
Microsoft	Yes	Yes	Yes	Yes	No	No	Yes	Yes
Google	Yes	Yes	No	Yes	No	No	Yes	Yes