REST stands for Representational State Transfer protocol. Roy Fielding defined REST in his PhD dissertation in 2000.

What is a REST API?

REST was developed to provide a uniform interface for

  • Identifying resources
  • Manipulation of resources
  • Self descriptive messages
  • Using Hypermedia as the Engine of Application State (HATEOS)

Best Practices


Method || http://api.co/v2/cars || http://api.co/v2/cars/1234

  • GET || List all the cars ||   Retrieve an individual car
  • POST || Create a new car     || Error
  • PUT || Replace cars collections  ||  Replace the car with id 1234
    with new one
  • DELETE ||       Delete all cars ||   Delete car with id 1234

Note while PUT operations either client or server can generate id’s

Nouns are good Verbs are bad

  • Use nouns to refer resources like cars, fruits etc.
  • Use verbs for action declarations convertMilesToKms, getNutritionalValues

Singular or Plural?

Use correct grammar for declaration

Avoid /person/145

Prefer /people/154 Assume to return 154th person from list of people

Use cases

Use anyone of the below patterns and be consistent!

Case StylesExampleUpperCamelCasehttp://api.fintech.cp/DailyTransactions/TodaylowerCamelCasehttp://api.fintech.cp/dailyTransactions/todaysnake_casehttp://api.fintech.cp/daily_transactions/today

Relationships and Resources

  • Resources can have one-to-many, many-to-many, many-to-one relationships etc. Mapping them correctly is crucial.

One-to-Many Mapping

For example, Tickets/145/messages/4 suggests one-to-many relationship between tickets and messages. Meaning 1 ticket has N messages. Message isn’t standalone resource. You can’t have /messages/4.

Many to Many Mapping

For example, /usergroups/345/users/56 suggests select 345th user group and get user with id 56. However, one user might be in multiple usergroups i.e. /usergroups/209/users/56 is also valid. In such case so for seperating the depedant resource users into a seperate endpoint like /users/56 and provide resource linking in /usergroups/209/users/56

API Parameters

  • PATH : required to access the resource E.g. /cars, /fruits
  • Query Parameters : optional filter the list E.g. /cars?type=SUV&year=2010
  • Body : Resource specific logic. Advance search query. Sometimes it might have both Query and body.
  • Header : Should contain global or platform wide data. E.g. API key parameters, encrypted keys for auth, device type information e.g. mobile or desktop or endpoint, device data type e.g. xml or json. Use header to communicate these parameters

HTTP Status Codes

Use correct status codes

CodesMeaning1xxRequest received and understood.2xxAction requested by client was received, understood and requested.3xxClient must take additional action to complete the request. Most of these status codes are used in URL Redirection.4xxIntended for situations where it seems the error was caused by the client.5xxThe server failed to fulfil a request.

Little more on 2xx!

  • 201 Resource Created. POST /cars should return HTTP 201 created with location header stating how to access the resource E.g. location : api.com/cars/124 in header

202 - Accepted

Use this if the task is huge to run. Tell the client, it has accepted the request and will/is process/processing No payload is returned

204 - No content

Used when deleted DELETE cars/124 Returns no content. But can also return 200 OK if API intends to send the deleted resource for further processing.

The dangerous 5xx resources!

  • 500 Internal Server Error
  • 504 Gateway Timeout. Server didn’t receive timely response

Less known 4xx suggests that you are passing wrong parameter. Can also pass information that is wrong. E.g.

DELETE /cars/MH09234

returns 4xx or message Expecting int car id /car/id got string car/MH09234