Hello, confirm that. Bug indeed. Also in my 41.0a2 any change (site changes) in browser.newtab.url bring me to the about:newtab page.

thank you

To ...update, please see : The browser.newtab.url preference is abused and should be removed (Bug 1118285)

see also : Bug 1179101 - NewTabURL object doesn't work in mozilla.cfg configuration file

(please do not comment in bug reports)

thank you

Note that you can re-add support for the browser.newtab.url pref via this code in the mozilla.cfg file.

• http://kb.mozillazine.org/Locking_preferences

You can consider to use a modified pref name like browser.newtab.URL in order not to defeat this change.

//
try{
 var newTabURL = getPref("browser.newtab.url");
 Components.utils.import("resource:///modules/NewTabURL.jsm");
 NewTabURL.override(newTabURL);
}
catch(e){}

Use this command in the Browser Console (Firefox/Tools > Web Developer) to set the new tab page from the browser.newtab.URL pref during Firefox runtime.

• https://developer.mozilla.org/Tools/Browser_Console#Browser_Console_command_line

newTabURL = Cc["@mozilla.org/preferences-service;1"].getService(Ci.nsIPrefService)
.QueryInterface(Ci.nsIPrefBranch2).getCharPref("browser.newtab.url");
NewTabURL.override(newTabURL);

An extension that you can use instead:

• New Tab Override (browser.newtab.url replacement): https://addons.mozilla.org/firefox/addon/new-tab-override/

cor-el you are awesome, thanks :-):-)