How to Turn Off Siri
To disable Siri on an iOS device running iOS 11 or above, go to Settings > Siri & Search and turn off each of the following (the buttons will turn white when disabled): Listen for “Hey Siri”, Press Home for Siri, and (if you see it) Allow Siri When Locked. Confirm with Turn Off Siri.
How to Turn off Siri (iOS 10)
Turning Siri off on iOS 10 involves a slightly different process. Go to Settings > General > Siri, and toggle off Siri. Tap Turn Off Siri when asked to confirm your choice.
How to Disable Dictation Features on iOS
Since disabling Siri means losing the ability to use voice commands on an iOS device, it makes sense to disable the Dictation function on your iOS device as well since it won’t work anymore. This is also necessary if you wish to remove all of your voice data from Apple’s servers.
How to Disable Siri on macOS
Disabling Siri on a Mac is also fairly straightforward.
How to Disable Dictation Features on macOS
Like Siri on iOS, disabling Siri on macOS doesn’t automatically remove all of your voice data from Apple’s servers. For that, you have to turn off dictation. Go to the Apple menu, select System Preferences, choose Keyboard, then select the Dictation tab to turn the feature off.