You can send data to the server in the body of the HTTP POST message. The type and size of data are not limited. But you must specify the data type in the Content-Type header and the data size in the Content-Length header fields. POST requests can also 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 POST method is not idempotent, which means that sending an identical POST request multiple times may additionally affect the state or cause further side effects (eg. on financial transactions).
The following example demonstrates sending a POST request to the server:
And the server response:
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
|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|
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 PUTThe 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.