These are the instructions to flash stock ROM (firmware) on Google Nexus Device using the Windows Computer.
Requirements: Your Google Nexus device should have at least 20-30 percent of battery to perform the flashing process.
Flash stock ROM (firmware) on Google Nexus Device
Download and install Google Nexus USB drivers on your computer.
Download and install Minimal ADB and fastboot tool on your computer.
Download the Google Nexus Stock ROM for your device.
- After Downloading the firmware, you need to extract it on your computer. After extracting you will be able to see the following files:
- Now, enable USB Debugging on your Nexus Device. To enable the USB debugging: Open Settings > Developer Options > USB Debugging > Tap on the Checkbox to Enable it.
(Developer Options is hidden for Android 4.2.2 or above, to show this option Go to Settings > About Phone > Built Number > Tap on it for 5-8 times).
- Now, Power off your Google Nexus Device.
- Now, you need to boot your device into the fastboot mode. For that press and hold Volume Down + Power for 7-10 seconds until fastboot mode is enabled.
- Now, connect your Nexus Device to the computer using the data cable.
- Now, you need to unlock the bootloader (it can be locked later). To unlock the bootloader, Open MAF32.exe or py_cmd.exe from the Minimal ADB and fastboot folder (C:Program FilesMinimal ADB and Fastboot).
Step 10: Once, Command Window is launched, Give the following command: fastboot oem unlock
- Now, you will be able to see warning message on your device screen, Using your Volume UP button Select Yes to Continue.
- Now, as your device bootloader is unlocked you can flash the firmware. To flash the firmware, Go to the extracted files and open flash-all.bat
- Now, flashing process will begin, and it will hardly take 5-10 minutes to complete.
- To lock the bootloader again, Open py_cmd.exe from the Minimal ADB and fastboot folder (C:Program FilesMinimal ADB and Fastboot). And give the following command: fastboot oem lock
 Caution: Flashing the Stock firmware will delete your personal data, so take a backup of your personal data before proceeding.
 Google Nexus Pixel Stock Firmware: If you are looking for the original firmware for your device, then head over to Download Google Nexus Pixel Stock Firmware page.
 Google Nexus Pixel USB Driver: If you are looking for the original USB Driver for your device, then head over to Download Google Nexus Pixel USB Driver page.
 Credits: The above flashing instruction is provided by Google at the Factory Image for Nexus Device page. We made the instructions more noob friendly.