Siri’s default search engine is Bing and that wouldn’t be much of a problem, except there is no setting that allows you change it. However, this doesn’t mean you can’t search Google or Yahoo instead of Bing with Siri (and probably other search engines as well).
While Apple is committed to Bing, people still prefer to find online information with Google (over 70% of them, actually), and a smaller subset of users rely on Yahoo!. There’s no specific option you can enable to switch Siri to a search engine other than the default Bing but you can still ask the assistant to input your search query.
As a simple solution, you ask Siri to input your search query in another search engine such as Google or Yahoo. Here’s how to do it:
Search Google or Yahoo instead of Bing with Siri on iPhone or iPad
The first step is to launch Siri on your device which you can do by pressing and holding the Home button. If you have ‘Hey Siri’ turned on (you can enable it under Settings->General->Siri and toggle the switch next to ‘Hey Siri‘) there’s no need to long press the Home button.
To use Google instead of Bing, speak ‘Search Google for…’ followed by the keyword or phrase you want to use for the search.
To use Yahoo instead of Bing, say ‘Search Yahoo for…’ and then continue with the term or phrase for your search query.
If you don’t mention any particular search engine, Siri will use Bing by default. Bing search results will be shown on Siri’s screen while for Google or Yahoo they’ll be displayed in a Safari page. And since there’s no setting provided to change the default search engine, you’ll need to always specify the preferred one (when it’s not Bing of course).