Speaking about Firefox, it is insane how needlessly complicated it is to add new search engine to Firefox [1]
1. Open a new tab and type about:config in the address bar
2. In the search box type: browser.urlbar.update2.engineAliasRefresh
3. Click on the little + symbol on the right. It should look like after you pressed it: boolean true value
4. Go to firefox Settings → Search. Or enter this in the address bar: about:preferences#search
5. In the "Search Shortcuts" section you should notice a new "add" button. search add button
6. Press the add button and fill in the name, search engine url and a keyword(optional).
7. Go to the "Default Search Engine" section and select the engine you just added.
[1] https://superuser.com/questions/7327/how-to-add-a-custom-sea...