In what way do you get that search engine?

You can open the about:config page via the location/address bar and search for prefs that refer to Ecosia. You can reset user set (bold) prefs via the right-click context menu to the default value.

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config

Hi, could you describe in more detail where Ecosia is showing up now? For example:

• replaces your expected home page -- see:
  • Startup, home page, tabs, and download settings

• listed with your other search sites or took over as your default search engine -- see:
  • Use the search bar in Firefox (section on setting default search engine)

• replaces your expected new tab page (comments at the end)

• other...

If you are able to clean it but then it returns when you quit and start Firefox again, please see this article for suggestions: How to fix preferences that won't save.

Here's how you can change your new tab page:

(1) In a new tab, type or paste about:config in the address bar and press Enter/Return. Click the button promising to be careful.

(2) In the search box above the list, type or paste newtab and pause while the list is filtered

(3) Double-click the browser.newtab.url preference and enter your preferred page:

• Page thumbnails (default) => about:newtab
• Blank tab => about:blank
• Built-in Firefox home page => about:home
• Any other page => full URL to the page

Press Cmd+t to open a new tab and verify that it worked. Fixed?

Thanks to you both. about:config solved the problem!