nsITraceableChannel
netwerk/base/public/nsitraceablechannel.idlscriptable this interface is used to allow intercepting of http traffic.
... inherits from: nsisupports last changed in gecko 1.9.0.4 the typical way to use this interface is as follows: register for the "http-on-examine-response" notification to track all http responses; skip redirects (responsestatus = 3xx on nsihttpchannel), since otherwise you may end up with two listeners registered for a channel; qi the channel passed as the "subject" to your observer to nsitraceablechannel, and replace the default nsistreamlistener (that passes the data to the original requester - e.g.
... see nsitraceablechannel, intercept http traffic for a more detailed description with code samples.
...stener.onstoprequest(arequest, acontext, astatuscode); this.deferreddone.resolve(); }, queryinterface: function(aiid) { if (aiid.equals(ci.nsistreamlistener) || aiid.equals(ci.nsisupports)) { return this; } throw cr.ns_nointerface; } }; var httpresponseobserver = { observe: function(asubject, atopic, adata) { var newlistener = new tracinglistener(); asubject.queryinterface(ci.nsitraceablechannel); newlistener.originallistener = asubject.setnewlistener(newlistener); /////// end - do not edit newlistener.promisedone.then( function() { // no error happened console.log('yay response done:', newlistener.responsebody); }, function(areason) { // promise was rejected, right now i didnt set up rejection, but i should listen to on abort or bade status code then reject mayb...

Intercepting Page Loads - Archive of obsolete content
you can also use these in conjunction with nsitraceablechannel to get and modify the response text before it gets to the original requester.

Index
1018 nsitraceablechannel http, interfaces, interfaces:scriptable, xpcom, xpcom interface reference the typical way to use this interface is as follows: 1019 nsitransaction interfaces, interfaces:scriptable, xpcom, xpcom interface reference executes the transaction.

Observer Notifications
the response can be accessed and modified via nsitraceablechannel.

XPCOM Interface Reference
reviewnsitaskbarpreviewbuttonnsitaskbarpreviewcontrollernsitaskbarprogressnsitaskbartabpreviewnsitaskbarwindowpreviewnsitelemetrynsitextinputprocessornsitextinputprocessorcallbacknsitextinputprocessornotificationnsithreadnsithreadeventfilternsithreadinternalnsithreadmanagernsithreadobservernsithreadpoolnsithreadpoollistenernsitimernsitimercallbacknsitoolkitnsitoolkitprofilensitoolkitprofileservicensitraceablechannelnsitransactionnsitransactionlistnsitransactionlistenernsitransactionmanagernsitransferablensitransportnsitransporteventsinknsitransportsecurityinfonsitreeboxobjectnsitreecolumnnsitreecolumnsnsitreecontentviewnsitreeselectionnsitreeviewnsiurinsiurifixupnsiurifixupinfonsiurlnsiurlformatternsiurlparsernsiutf8converterservicensiutf8stringenumeratornsiuuidgeneratornsiupdatensiupdatechecklistenernsiupda...

XPCOM Interface Reference by grouping
nsicryptohash filter nsiparentalcontrolsservice nsipermission nsipermissionmanager nsisecuritycheckedcomponent ssl nsisslerrorlistener stream stream nsipipe nsitraceablechannel nsitransport nsitransporteventsink nsitransportsecurityinfo timer nsitimer nsitimercallback ui windows nsitaskbarpreview nsitaskbarpreviewbutton nsitaskbarpreviewcontroller nsitaskbarprogress nsitaskbartabpreview nsit...