Since OnePlus One is no longer receiving official updates from OnePlus, but thanks to the XDA-Developers, Android Oreo is available for OnePlus One. Follow this guide for features and steps to update OnePlus One to Android 8.0 Oreo based custom ROM.

Prerequisites to install Android 8.0 Oreo ROM on OnePlus One

  • Download and install USB drivers for OnePlus One on your computer.
  • Enable USB debugging option by pressing Menu > Settings > Applications. Navigate and tap on Developer Options to enable USB Debugging.
  • Your OnePlus One should be rooted.
  • Make sure to install TWRP or CWM recovery tool.
  • Ensure that your OnePlus One carries more than 70% of charge.

How to update OnePlus One to Android 8.0 Oreo ROM

Required files:
Download ROM :  (BasketBuild AndroidFileHost)
 Download Android Oreo Gapps

  • Connect your OnePlus One to your PC using USB cable and copy the downloaded files to the SD card of your device.
  • Disconnect your OnePlus One and power it off.
  • Now boot it into the recovery mode: press and hold Volume Up, Home and the Power buttons simultaneously. Use Volume keys to highlight and Power button to select.
  • In the TWRP/CWM settings menu, clear phone memory: go to Wipe > Full Wipe.
  • Return to TWRP settings and tap Install and locate the Android 8.0 Oreo firmware zip file from the phone memory.
  • In the menu, confirm the installation process by tapping Swipe to Confirm Flash.
  • Your phone will now install the Android 8.0 Oreo custom ROM.
  • When you receive the Successful message, you can restart your device.

First boot takes a little, so a little patience would go a long way.

Flash at your own risk!

Source: XDA-Developers