Firefox Add-on RESTclient — How to input POST parameters?

Here is a step by step guide (I think this should come pre-loaded with the add-on):

  1. In the top menu of RESTClient -> Headers -> Custom Header
  2. In the pop-up box, enter Name: Content-Type and Value: application/x-www-form-urlencoded
  3. Check the «Save to favourite» box and click Okay.
  4. Now you will see a «Headers» section with your newly added data.
  5. Then in the Body section, you can enter your data to post like: username=test&name=Firstname+Lastname
  6. Whenever you want to make a post request, from the Headers main menu, select the Content-Type:.. item that you added and it should work.

Hope this helps.