Check . If it says "Bootloader unlock allowed: No," QunlockTool is often the only way to change this to "Yes." Download and Setup :

qUnlockTool is not a one-click solution that you can just download and run for free. It is a commercial product that operates on a client-server model, meaning each unlock attempt requires an online connection to the tool's central server to function.

: Backup your data and charge the phone to at least 50%. Step-by-Step Guide

qUnlockTool was once a legendary piece of software in the Sony Xperia modding community. It provided the only viable pathway for thousands of users to escape the strict bootloader restrictions imposed by Japanese carriers, turning their carrier-subsidized phones into fully unlocked developer devices. For a fee of around $25, it worked like magic, flipping the "No" to a "Yes".

In the world of Android devices, Sony has established itself as a reputable brand, known for producing high-quality smartphones and tablets. However, as with any Android device, users often seek to unlock the full potential of their Sony device, experimenting with custom ROMs, kernels, and other modifications. One popular tool that has gained significant attention in recent years is the QUnlockTool, specifically designed for Sony devices. In this detailed blog post, we'll explore the world of QUnlockTool and its capabilities.

However, users should be aware that recent reports from platforms like indicate that the qUnlockTool servers are currently offline

Sony Xperia Phone - Service / Test Menu - iFixit Repair Guide