When a manufacturer releases a system update, there is a general assumption that the update will not break everything. If you have a Pixel C that hasn't received the Android 8.1 update yet (or you've been holding off), consider yourself lucky - many users discovered that the OTA triggered a factory reset.

Google released the final build of Android 8.1 earlier this week, and the update started to roll out to Nexus and Pixel devices worldwide (including the Pixel C). Unfortunately, after installing the OTA, some users discovered their tablets had been wiped.

There are multiple reports on Twitter (some of which are embedded above), the Pixel C subreddit, and the official Nexus Help Forum. While no explanation of the cause was provided, a Google Community Manager said the issue has now been resolved:

Hey All,

We've fixed the issue that caused this. Resetting your device will let you restore a backup, if your automatic backup feature was on. For instructions for resetting your device, please see this article.

We apologize for the inconvenience.

If you update your Pixel C now, it (probably) won't be reset in the process. You can find the Community Manager's reply at the source link below.