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+).

You read my question backwards. (I realize it's an easily misunderstood question, no worries)

I don't want to make new tab be my homepage; I want to make my homepage be the stuff that normally shows on a new tab.

You can set the startup (home) page to about:newtab

• Tools > Options > General > Startup: Home page
• https://support.mozilla.org/kb/How+to+set+the+home+page

Note that Firefox supports multiple home pages separated by '|' (pipe) symbols.

You can use pages like these:

• the default new tab page with the tiles is about:newtab
• the default home page is about:home
• for a blank page use about:blank

Opps :-(