Unlocking the bootloader is not a task most Android users may want or need to undertake, as it comes with its fair share of risks, but it is paramount for those who want to install a different distribution, load a faster kernel, use a third-party recovery and so on. I personally prefer to turn off all the nannies on every Android device I own, as it makes way for quick modifications.
While not all manufacturers allow users to unlock the bootloader on their devices, there are a couple of vendors which believe this should be possible, and straightforward. Among them is Sony, known for its modder-friendly attitude, which has just improved its dedicated online tool for Xperia smartphones and tablets. And here is how easy it is to use.
To start off, you need to open Sony's Unlock your boot loader page. At the bottom, select your Xperia device from the list of compatible devices, then type in your email address to get the necessary code. You will have to validate this address, so check your inbox.
Then simply type in the IMEI number of your Xperia device, and hit the Submit button. The code that unlocks the bootloader will arrive via email. After that happens, simply use it as instructed to complete the process.
There are a couple of caveats with this tool, however. First off, the online tool does not work with all models of a compatible Xperia device (I can only presume that mobile operator-branded models are excluded). Secondly, this may or may not void the warranty. And finally, Sony says that a service fee may apply if it "does perform any warranty repairs" due to the "modified software". So bear all that in mind.