The browser.newtab.url pref is no longer supported in Firefox 41 and later, so you can no longer use this to set the new tab page.

You can look at this extension to set the new tab page:

• New Tab Override: https://addons.mozilla.org/firefox/addon/new-tab-override/

You can set the new tab URL setting via the Options/Preferences of the extension on the about:addons page.

Look at this extension to use the home page:

• New Tab Homepage: https://addons.mozilla.org/firefox/addon/new-tab-homepage/

Classic Theme Restorer includes this feature as well. In CTR version 1.3.9 you can find the "New tab page url" in the Tabs (1) window.

You can use these special pages for the new tab page or use the URL of a web page. the default new tab page with the tiles is about:newtab

• the default home page is about:home
• for a blank page you can use about:blank
• for Super Start you can use about:superstart

Isn't it about time to include this as an option within Firefox? How long do you plan to answer this question by telling people to go to about:config (which is no longer supported), or download an addon extension when this most basic of settings is even included in Internet Explorer!

Storing this setting as a pref that can be accessed via about:config has been removed because it is too easy for malware to abuse this.

You can still do this without using an extension, but it is more complicated as it involves running privileged JavaScript code.

You can run such JavaScript code via a mozilla.cfg file or during a session in the Browser Console.

You can open the Browser Console (3-bar Menu button or Tools > Web Developer). Toggle devtools.chrome.enabled to true on the about:config page to enable the command line in the Browser Console.

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

Paste the JavaScript code in the command line. Press the Enter key to evaluate the JavaScript code. You can use this command to check the current new tab setting:

• NewTabURL.get();

You can use this command to set the new tab URL:

• NewTabURL.override("about:blank");

A mozilla.cfg file in the Firefox program folder can be used to set and lock preference values and run privileged JavaScript code.

A local-settings.js file needs to be placed in the "defaults/pref" folder where also the channel-prefs.js file is located to specify using mozilla.cfg.

pref("general.config.filename", "mozilla.cfg");
pref("general.config.obscure_value", 0);

See Configuration:

• https://developer.mozilla.org/en-US/Firefox/Enterprise_deployment

Possible content of mozilla.cfg:

//
var newTabURL = "about:blank";
Cu.import("resource:///modules/NewTabURL.jsm");
NewTabURL.override(newTabURL);