The Android 8.1 beta OTA is beginning to roll out to users who have signed up for the beta program, following only a day after Google announced the Android 8.1 developer preview and published the system image for people to download and flash. For those who are familiar with flashing software to their phones, Android 8.1 has been available since yesterday, but for those who preferred to wait for a simple download and install process, it appears that the time to get their hands on the software is now. The update is guaranteed to be hitting at least some Google Pixel devices from 2016 but it's likely heading out to any compatible device which has been enrolled in the beta.
The update file is a fairly large one coming in at 948.5MB for the Pixel, and it should be about the same size for most other devices which are available to receive the update. That being said, you will want to make sure of a few things before proceeding if you do have the update available for download. First, you'll want to ensure that you have plenty of battery life for the download and installation to complete. Generally, this needs to be at least 50 percent, but if your device is plugged in then you'll also be fine. With this large of a file size you will also likely want to initiate and complete the download while connected to Wi-Fi and not cellular networks as it will be eating up near an entire 1GB of data.
Keeping those things in mind, it's important to remember that this is a beta. That means if you download and install the software, it's possible that you could run into issues with certain things not working or functioning correctly. This is what betas are for, so Google can catch these sorts of issues before rolling out a final software release to the public. If you're ok with that and want to go forward with the update, and even if you haven't seen a status alert coming through telling you the update is available, it may still be possible to pull the OTA down by navigating to settings, then to "system," and finally by tapping on the software updates button within that sub-menu. If it's available for you, the screen to start the process will show up.