Prerequisite

Download and Install Nexus USB drivers for your PC because you’ll be connecting your device with computer. Create a backup of all your important data like your Apps backup, contacts, Text data and other multimedia files. Charge your phone’s battery full or at least 70% to avoid any power shortage problem during the update. Enable USB debugging, go to settings > developers options > enable USB debugging. If you don’t see developers options in settings enable it in About Phone option by tapping build number for seven times. You should know how to use Android SDK or else this process is not recommended for you.

Disclaimer

This tutorial is only for Google Nexus 9, Do Not try this on any other device or else you may result end up bricking your device, follow the procedure carefully. Droidopinions.com will not be held responsible if somethinf goes with your device during or after the process. Try this at your own risk only.

Download these files

Android 6.0.1 Marshmallow MMB29K firmware Android SDK

Update Nexus 9 WiFi to Marshmallow 6.0.1

That is it. This was the manual method to update Google Nexus 9 WiFi to Marshmallow 6.0. Please share it and subscribe. Sharing buttons are below and subscription box is at the end.