The Fx0 is a high-end consumer Firefox OS smart phone, and marks the very first Firefox OS phone release in Japan. It was released by KDDI in December 2014.

Get a device

On release, the Fx0 was available to buy through standard Japanese retail channels. Being a SIM-locked device, it could only be used in Japan.

More recently (late 2015/early 2016), GSM unlocked phones became available, sold by various online shops.

Updating & upgrading the software

The device's system image is locked, so you can only update the software when the network operator releases an OTA update. The device system image is based on Firefox OS 2.0.

Device specifications

You can find more of the device specifications listed on our Phone and device specs page.


  • CPU: Qualcomm Snapdragon S4 MSM8926 1.2GHz quad-core
  • Camera: 8 megapixel front, 2.1 megapixel back
  • Battery: 2,370mAh
  • Display: 4.7"/IPS
  • Resolution: 1280 x 720
  • Internal memory: 16GB ROM, 1.5GB RAM   
  • External memory: microSDXC (64GB max.)
  • Size: 70x139x10.5 mm
  • Weight: Approx. 148g

See also