HTTP POST Requests

The HTTP POST method is used to send data to the server, or to create/update a resource.
Unlike GET and HEAD requests, the POST requests may change the server state.

The POST requests can have a message body. The size of the message body is not limited.
And you also can send data to the server using the URL parameters. In this case, you are limited to the maximum size of the URL, which is about 2000 characters (it depends on the browser).

The following example demonstrates adding a new order using the POST method:

POST /api/v1/orders HTTP/1.1
Authorization: Bearer mt0dgHmLJMVQhvjpNXDyA83vA_PxH23Y
Accept: application/json
Content-Type: application/json
Content-Length: 70
Host: myserver.com

{
  "Sku": "20223", 
  "Name": "John Smith", 
  "Price": "10.00"
}
And the server response:

HTTP/1.1 200 OK
Content-Length: 0
Some notes on POST requests:
  • POST requests are never cached
  • POST requests do not remain in the browser history
  • POST requests cannot be bookmarked

GET vs POST

GET POST
Browser BACK button/Reload Harmless Data will be re-submitted (the browser should alert the user that the data are about to be re-submitted)
Bookmarked Can be bookmarked Cannot be bookmarked
Cached Can be cached Not cached
History Parameters remain in browser history Parameters are not saved in browser history
Restrictions on data length Yes, when sending data, the GET method adds the data to the URL; and the length of a URL is limited (maximum URL length is 2048 characters) No restrictions
Restrictions on data type Only ASCII characters allowed No restrictions. Binary data is also allowed
Security GET is less secure compared to POST because data sent is part of the URL

Never use GET when sending passwords or other sensitive information!
Visibility Data is visible to everyone in the URL Data is not displayed in the URL

POST vs PUT

The fundamental difference between the POST and PUT requests is reflected in the different meaning of the Request-URI. The URI in a POST request identifies the resource that will handle the enclosed entity. In contrast; the URI in a PUT request identifies the entity enclosed with the request. Practically speaking, POST is used to append a resource to an existing collection, while PUT is used to update an existing resource.

To read more about HTTP POST method please check RFC2616.