POST

The POST HTTP method sends data to the server. The type of the body of the request is indicated by the Content-Type header.

The difference between PUT and POST is that PUT is idempotent: calling it once is no different from calling it several times successively (there are no side effects). Successive identical POST requests may have additional effects, such as creating the same order several times.

HTML forms typically send data using POST and this usually results in a change on the server. For HTML forms the format/encoding of the body content is determined by the enctype attribute of the <form> element or the formenctype attribute of the <input> or <button> elements. The encoding may be one of the following:

• application/x-www-form-urlencoded: the keys and values are encoded in key-value tuples separated by an ampersand (&), with an equals symbol (=) between the key and the value (e.g., first-name=Frida&last-name=Kahlo). Non-alphanumeric characters in both keys and values are percent-encoded: this is the reason why this type is not suitable to use with binary data and you should use multipart/form-data for this purpose instead.
• multipart/form-data: each value is sent as a block of data ("body part"), with a user agent-defined delimiter (for example, boundary="delimiter12345") separating each part. The keys are described in the Content-Disposition header of each part or block of data.
• text/plain

When the POST request is sent following a fetch() call, or for any other reason than an HTML form, the body can be any type. As described in the HTTP 1.1 specification, POST is designed to allow a uniform method to cover the following functions:

• Annotation of existing resources
• Posting a message to a bulletin board, newsgroup, mailing list, or similar group of articles
• Adding a new user through a signup form
• Providing a block of data, such as the result of submitting a form, to a data-handling process
• Extending a database through an append operation

Request has body	Yes
Successful response has body	Yes
Safe	No
Idempotent	No
Cacheable	Only if freshness information is included
Allowed in HTML forms	Yes

POST <request-target>["?"<query>] HTTP/1.1

POST /test HTTP/1.1
Host: example.com
Content-Type: application/x-www-form-urlencoded
Content-Length: 27

field1=value1&field2=value2

POST /test HTTP/1.1
Host: example.com
Content-Type: multipart/form-data;boundary="delimiter12345"

--delimiter12345
Content-Disposition: form-data; name="field1"

value1
--delimiter12345
Content-Disposition: form-data; name="field2"; filename="example.txt"

value2
--delimiter12345--