http - Are the PUT, DELETE, HEAD, etc methods available in most web browsers?

I've seen a couple questions around here like How to debug RESTful services, which mentions:

Unfortunately that same browser won't allow me to test HTTP PUT, DELETE, and to a certain degree even HTTP POST.

I've also heard that browsers support only GET and POST, from some other sources like:

However, a few quick tests in Firefox show that sending PUT and DELETE requests works as expected -- the XMLHttpRequest completes successfully, and the request shows up in the server logs with the right method. Is there some aspect to this I'm missing, such as cross-browser compatibility or non-obvious limitations?

Answer

No. The HTML 5 spec mentions:

The method and formmethod content attributes are enumerated attributes
with the following keywords and states:

The keyword get, mapping to the state GET, indicating the HTTP GET
method. The GET method should only request and retrieve data and
should have no other effect.

The keyword post, mapping to the state
POST, indicating the HTTP POST method. The POST method requests that
the server accept the submitted form's data to be processed, which may
result in an item being added to a database, the creation of a new web
page resource, the updating of the existing page, or all of the
mentioned outcomes.

The keyword dialog, mapping to the state dialog, indicating that
submitting the form is intended to close the dialog box in which the
form finds itself, if any, and otherwise not submit.

The invalid value default for these attributes is the GET state

I.e. HTML forms only support GET and POST as HTTP request methods. A workaround for this is to tunnel other methods through POST by using a hidden form field which is read by the server and the request dispatched accordingly.

However, GET, POST, PUT and DELETE are supported by the implementations of XMLHttpRequest (i.e. AJAX calls) in all the major web browsers (IE, Firefox, Safari, Chrome, Opera).