Cortana is mandatory in the Windows 10 Anniversary Update
Microsoft knows you'll love its digital assistant -- because now you have to.

I hope you're excited about the new features and functionality Cortana is getting in the Windows 10 Anniversary Update, because Microsoft is making its digital assistant an integral part of the operating system. And by "integral," of course I mean "mandatory," because once the update hits on August 2, users will no longer be able to turn Cortana off.
In the Windows 10 Anniversary Update, Cortana is synonymous with search. If you use the search box to look for a file on your device, you'll be using Cortana. What this means is that searches you perform will be filtered through the web (using Bing, of course), and usage data will be periodically sent to Microsoft.
I know this probably sounds terrifying, but it's not actually a huge change, privacy-wise, from how Windows 10 already works. Windows 10 already collects data from all users, especially if you use any of Microsoft's cloud-based services -- including signing into your device via a Microsoft account. Microsoft's mandatory data collection is a privacy concern, but it was a privacy concern long before they removed Cortana's off switch. You can, of course, refuse to sign into Cortana or Windows 10 with a Microsoft account. But your usage data will still be collected, albeit anonymously.
The good news is that you can limit Cortana's access to your private data so that she functions more like a simple search box than a nosy personal assistant. You can stop her from collecting information about your speech, handwriting patterns and typing history, and you can stop her from saving your habitual usage data across multiple devices. Here's how:
Disable Cortana's settings
Open Cortana and click the settings icon in the lower left corner to open Cortana's settings menu. You'll see several options with on/off toggles -- turn all those toggles to off. This will prevent Cortana from sharing your usage history across devices and from syncing notifications and other settings across devices.
If you use Cortana to search after disabling these settings, your data may still be sent to Microsoft but won't be saved and shared across your devices.
Wipe Cortana's memory
Once you've disabled Cortana's settings, you can clear the information she's already collected about you by opening Cortana, clicking the settings icon, and clicking Change what Cortana knows about me in the cloud. Scroll to the bottom of the next screen and click Clear.
You can also clear your Bing search history by going to Cortana settings > Change what Cortana knows about me in the cloud and clicking Search History page under Where else is Cortana saving data about you.
Stop 'Getting to know you'
Cortana collects information about you -- by listening to your voice and tracking your handwriting patterns and typing history -- to help improve your personalized experience. To turn this off, open the Settings menu and go to Privacy > Speech, inking, & typing. Click Stop getting to know me to stop Cortana from collecting this info and to clear any information she's already collected.
Hide the Cortana button
If you don't plan on using Cortana or search at all in Windows 10, you can hide the Cortana button from your taskbar. To do this, right-click the taskbar, go to Cortana and click Hidden.
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