Hold the button while connecting the USB cable to the PC to enter "Flash mode".
On many Sony devices, checking the service menu reveals "Bootloader unlock allowed: No." The S1 Unlock Tool can sometimes flip this bit, allowing users to install custom ROMs like LineageOS. ⚡ Dead Phone Repair s1 unlock tool sony
: Historically, this was not a free tool. Users had to purchase "credits" (roughly $20–$30) from third-party resellers to perform the unlock. Hold the button while connecting the USB cable
For most Sony Xperia devices, the is available via Sony’s website: s1 unlock tool sony
: Once the software detects your device, select the "Unlock" or "Check Credit" button to begin the automated process. Comparison: Official Bootloader Unlocking vs. S1 Tool