When do you use "GET" vs. "POST"

The HTTP specifications technically define the difference between "GET" and "POST" so that former means that form data is to be encoded (by a browser) into a URL while the latter means that the form data is to appear within a message body. But the specifications also give the usage recommendation that the "GET" method should be used when the form processing is "idempotent" (i.e., it has no lasting observable effect on the state of the world), and in those cases only. As a simplification, we might say that "GET" is basically for just getting (retrieving) data whereas "POST" may involve anything, like storing or updating data, or ordering a product, or sending E-mail.

See as reference http://www.cs.tut.fi/~jkorpela/forms/methods.html

This information is offered for those who want or need a general understanding of these two commands used in communications between a browser and a server - for example, communication with the Prevent or Monitor servers.

For more information, please see related article "How can I monitor HTTP GETs on a Network Monitor?".