Download Android 4.4 Kitkat stock firmware for OnePlus One

 

Download Android 4.4 Kitkat stock firmware for OnePlus One from here, here or from here. File name: aosp-One-ota-20140719.zip (231 MB)

Instructions​

1. Place the downloaded .zip somewhere easily accessible on your phone  
2. Unlock bootloader and acquire custom recovery from here.  
3. Reboot to recovery (power off, then power + volume down until it vibrates)
4. Wipe your device (incl. cache & dalvik)  
5. Flash the .zip. Flash Gapps - gapps-kk-20140606-signed.zip
6. Reboot

General
- Warranty info: Doing this does not void your warranty. If you brick your phone, however, you're on your own. We will repair it, but that's not covered by warranty.
- Please don't use toolkits. Learning how this works is good for you.

Known issues
- Gyroscope may not work for all devices
- Encryption features and VPN do not work
There may be more - with the help of you, our bleeding-edge users, we’ll be able to improve this product until it’s 100% stable and beyond. 

via forums.oneplus.net