Firefox for iOS gives you the ability to add, remove and change a default search engine. There are a variety of search engines available to choose from such as Google and Bing. You can also manually add other search engines and set one of them as your default.

Change default search engine

1. At the bottom of the screen, tap the menu button (the menu will be at the top right if you're using an iPad):
   

2. Tap Settings in the menu panel.
3. Tap Search.
4. Tap the current default search engine name.
5. You current default search engine choice will have a check mark. To use another, tap the name of the search you want to use as your default search engine.
6. After you select a new default search engine, Firefox will take you back to the Search screen. Tap Settings to return to the menu, and tap Done to close it.

Add a search engine

1. At the bottom of the screen, tap the menu button (the menu will be at the top right if you're using an iPad):
   

2. Tap Settings in the menu panel.
3. Tap Search.
4. Tap Add Search Engine under the list of available Quick-Search Engines.
5. Enter a name for the search engine in the Title text field.
6. Enter a search string URL in the URL text field.

   Note: Please be sure to replace the query string with “%s”, for example:
   https://www.google.com/search?q=%s
   https://www.startpage.com/sp/search?q=%s
   https://www.ecosia.org/search?q=%s
   
   If you don't know which search string to use for a particular search engine, you can access its website in a new tab, do any search and use the resulting URL as a reference. For example, if you go to ecosia.org and search for firefox, the resulting URL in the address bar will be https://www.ecosia.org/search?q=firefox. Then the search string must be https://www.ecosia.org/search?q=%s, replacing the query with "%s".

7. Tap the Save button. The search engine is added to the predefined list of search engines in alphabetical order.