With Firefox 41 (and higher), it's no longer possible to customize the page shown in a new tab via changing the preference browser.newtab.url in about:config. Because of the fact that hijackers abused the preference in the past, Mozilla decided to remove it (see bug 1118285). Fortunately, by removing it, Mozilla also introduced a new API to bring this functionality back to life as an add-on. This add-on allows the user to choose a certain page in a new tab.

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

This is also available using Classic Theme Restorer (Customize Australis) {web link} Restore squared tabs, appmenu, add-ons bar, small button view and more on Australis UI (Windows/MacOSX/Linux + Fx 29+).

Sorry, new-tab-override/ doesn't seem to achieve what I want. If I set it to about:newtab (Default) then a new Tab opens as in pic 1 below; which is what I want. But a new window opens like pic 2. But I want it, also, to open as pic 1. Ta

If your intention is to have the start page displayed as a new tab and its Top Sites as your first image shows, you can just enter about:newtab in the Preferences > General > Home Page field of the Startup section.

That should cause a new window to "follow" your New Tab settings as configured in the cogwheel in the top right of a new tab page, so whenever you set that to a blank page, the same will apply to new windows. (Also, that cogwheel will be available on every new page when set.)

A new window opens with the home page(s). You would have to set the home page to a blank page (about:blank) or create a bookmark on the Bookmarks Toolbar that opens the about:blank page. You would have to hold the Shift key to open a new window with a left-click.

Thanks. Got it!

Hello,

I am glad to hear that your problem has been resolved. If you haven't already, please select the answer that solves the problem. This will help other users with similar problems find the solution more easily.

Thank you for contacting Mozilla Support.

Sorry, but I’m afraid the wrong or at least not the best answer has been marked as solution (but correct me if I’m wrong.)

The user does not only want a blank page to be opened in a new window like the question says, which of course is a matter of choosing so in the Home Page section in Options/Preferences.

What he/she rather wants, also looking at the " ... pic 1 below; which is what I want" comment, is the exact same behavior for new windows and new tabs, which can both be a blank page and a page displaying Top Sites (including suggested sites if configured), both with the cursor in the URL field.

The way to achieve that is to set the Home Page to about:newtab AND NOT to Show a blank page in the Startup section but one of the other two options - I should have added that above. When set as such, a new window will behave similar to a new tab as set in the New Tab page config (the cogwheel) so the choice made there will be valid for both, and no workaround or add-ons are required.