Made My Own Arduino Board - ATMEGA32U4 - Bootloader Questions

Other Hardware 3rd Party Boards
4

This file:

https://github.com/arduino/Arduino/blob/master/hardware/arduino/bootloaders/caterina/Caterina-Leonardo.hex

seems to have a lot of 0xFF in it. It looks a bit like it also contains some default sketch.

Once you get past all that it seems to have code at 0x7000 to 0x8000 which would be 4096 bytes (4K) which sounds right for a bootloader.