In most Android devices, unlocking the bootloader means getting unrestricted access to flashing ROMs, custom kernels and other mods. However, on HTC devices, users will need to gain S-OFF if they want complete freedom while tinkering with their device. So what exactly is S-OFF? How does it benefit the end user? Read below to find out.
By default, HTC devices come with an S-ON flag, which stands for Security-On. This protects certain portions of the NAND, on which the OS and other firmware for other components reside, from being modified permanently or even being touched. Any change that you make with S-ON will automatically be lost when the phone reboots. On pre-HTC One M7 devices, this even includes the kernel partition. Also, any firmware that you want to flash on your device must be signed by HTC.
With this security turned off, users can tinker around with some low-level hardware stuff like changing the firmware of the audio system, its variant and more. For example, owners of HTC One M7/M8 can convert their device into a Google Play one and even receive direct OTA updates from Google, if they are ready to S-OFF it and change its CID and MID values. Other benefits of S-OFF include the ability to reset the bootloader/tampered status of the phone, and flash non-signed (leaked) firmwares from HTC.
Keep in mind that S-OFF has nothing to do with root access. You can easily gain root access on any HTC device by unlocking its bootloader first and then installing SuperSU. Usually, you will need root access to gain S-OFF on any HTC device. However, in certain cases and handsets, users can actually gain S-OFF first and then unlock the bootloader without using HTC’s bootloader unlock tool or wiping the internal memory of the device. One M8 users, for example, can actually gain S-OFF, root access and even unlock the bootloader of their device by using Sunshine, which does not even require users to be near a PC. It does cost $25 though, which not be appreciated by everyone.
In the end, if you are a normal user, simply gaining root access on your HTC device will be more than enough for you. However, if you want to jump into some low-level mods, you will have to eventually gain S-OFF on your HTC device.
