To keep your search history off the record, start by opening up the app, tapping on your display picture in the upper-left corner, then hitting ‘Turn on Incognito.’
Alternatively, if your device features 3D Touch , you can toggle an Incognito browser session by hard pressing the Search icon on the home screen.
However, Incognito searches can be guarded by TouchID — so you can leave the the app and come back to it knowing that nobody has taken a glance of what you are searching.
Google also said that it has made a handful of other changes to Search. The most notable of which is the facility to watch YouTube videos within the app.