TIL: 8 versions of UUID and when to use them | nicole@web

In legacy serialization, the marker byte would have been interpreted as the number of inputs (zero). A transaction can’t have zero inputs, so the marker signals to modern programs that extended serialization is being used. The flag field provides a similar signal and also simplifies the process of updating the serialization format in the future.

P2PKH and P2SH are the only two script templates used with base58check encoding. They are now known as legacy addresses and have become less common over time. Legacy addresses were supplanted by the bech32 family of addresses.