Comment by mebeim

The homepage loads exactly the most common x86-64 ABI, which is x64 (according to kernel naming). It's the one for 64-bit syscalls made by 64-bit code. On x86-64 you also have IA32 (32-bit syscalls made by 32-bit code) and x32 (64-bit syscalls made by 64-bit code specifically built to only use 32-bit pointers).