First unveiled back in March as an early preview, Android O Beta is now live and available for all eligible Nexus and Pixel devices. Android O is the next major Android update, which offers various new features, performance enhancements and better battery life. Android O Beta program is available for Nexus 5X, Nexus 6P, Pixel, Pixel XL, Pixel C and Nexus Player. Interested users can enroll for Android O beta program here to get the OTA update.
Note that this is the second developer preview of Android O (OOP2), which weighs around 1GB. Users who are opt-in for Android Beta program will get the OTA update that updates your device to Android O DP2 without losing data. If you prefer manual installation, factory images for Android O Developer Preview 2 are now available at Android O downloads page. Android O DP2 OTA files can be downloaded from here.
Note: Users, who were signed up for the previous Android N Beta Program need to re-enroll into the Android O Beta Program to get the OTA update.
Remember that installing Android O Beta OTA update will not wipe your device. However, if you want to roll back to the previous stable version of Android, your device will be formatted.
Note that this is an early preview of Android O, which is not perfect for daily use, as it contain bugs and performance issues. Uses are advices to wait for the final release, which will be released sometimes in Q3 of this year 2017.