In computing, a POST message is a type of HTTP request message. It is used when the request should result in an action on the server which has side effects. For example, when submitting a form to buy something on a website a POST method is normally used.

Because POST requests typically have side effects, they are, by default, not cached. This differs from the default behavior of GET requests.

The term itself presumably originates from the act "posting" a message to a bulletin board, newsgroup, mailing list, etc.

[edit] Request body

A POST request includes a message body in addition to a URL used to specify information for the action being performed. This body can use any encoding, but when web browsers send POST requests from an HTML form element the Internet media type is "application/x-www-form-urlencoded". ^[1]

This is a format for encoding key-value pairs with possibly duplicate keys. Each key-value pair is separated by an '&' character, and each key is separated from its value by an '=' character. Keys and values are both escaped by replacing spaces with the '+' character and then using URL encoding on all other characters.

For example, the key-value pairs

 Name: Jonathan Doe Age: 23 Formula: a + b == 13%! 

are encoded as

 Name=Jonathan+Doe&Age=23&Formula=a+%2B+b+%3D%3D+13%25%21 

[edit] References

[edit] External links

• Straightforward definition of POST
• POST verb in HTTP specification
• URIs, Addressability, and the use of HTTP GET and POST