Mozilla (stylized as moz://a) is a free software community founded in 1998 by members of Netscape.
Modifying such headers is forbidden because the user agent retains full control over them. Names starting with
Forbidden header names start with
, or are one of the following names:
header is no longer forbidden, as per spec — see forbidden header name list (this was implemented in Firefox 43) — it can now be set in a Fetch Headers object, or via XHR setRequestHeader(). However, Chrome will silently drop the header from Fetch requests (see Chromium bug 571722).