Owners of Sony Xperia Z3 and Xperia Z3 Compact Android handsets that have a locked bootloader, it is your lucky day. At least, it is if you’ve been hoping to root your device.
A clever dev over at the XDA-Forums has scored himself a touch of bounty for working out the xploit. Sorry… exploit. The method is not intended for the international Xperia Z3 and Z3 Compact devices, which come with unlockable bootloaders, and are rather easily tinkered with by the AOSP and ROM enthusiasts. Nor is it for the Verizon variants with modified hardware. Instead, the exploit is for markets like the U.S. where carriers tend to lock things down.
Let’s not beat around the bush here, with Android Lollipop set to release for Sony hardware soon, You are likely better off waiting for the OTA before rooting. Also, this is not an easy process. Right off the bat, up to date firmware is not compatible, so you’ll need to first roll back to version 23.0.1.A.5.77. From there, it is a matter of simply creating a pre-rooted version of the phone’s hardware, flash a recovery image for your model, then apply the root exploit itself.

XDA user zxz0O0 is who you have to thank for bringing root to your locked Sony Xperia Z3 or Xperia Z3 Compact. He’s been known to bring exploit and similar tools to the forums and will take home at least a part of the current $3017 bounty available for breaking the lock on Sony gear.
Head on over to the XDA post on the matter to get all the resources and instructions to root your Sony Xperia Z3 and Xperia Z3 Compact handsets.