Samsung bootloader bit: can I downgrade?

Samsung uses an anti-rollback counter, the bootloader (binary) bit. It sits in the 5th-last character of every build number. A device only accepts firmware whose bit is equal to or higher than the bit it currently runs.

How to read it

In A546BXXUNGZJ5 the bit is N. Digits count as themselves, letters continue after 9: A = 10, B = 11 … N = 23. Our model pages show the bit of every build in the Bit column.

The rules

• Same bit: downgrading is possible, for example from a November to a September build with the same bit.
• Lower bit: blocked. Odin stops with an error such as “
  ”. There is no safe workaround.
• Higher bit: always fine, that is a normal update – but afterwards every build with the old bit is locked out for good.

Check before you update

If you might want to go back – for example because of a bug or a removed feature – look at the model page first: when the next build raises the bit, everything before it becomes unreachable. Security patches sometimes raise the bit without any new Android version.

Bit vs. Android version

The bit is independent of the Android version. A device can receive several Android upgrades on the same bit, and a bit increase can arrive with a small security update. Always compare the bit, not the Android number.