Bitcoin Legacy address is an older version of address formats used in Bitcoin. It was the first address format used in Bitcoin after the release of its original software. This address format uses a “Base58Check” encoding system which is a combination of Base58 encoding and a checksum.
This system allows Bitcoin wallets to detect errors in address strings and reject those that are malformed. A Bitcoin Legacy Address consists of a random string of letters and numbers, usually beginning with the number ‘1’ and most consisting of 34 characters in length.
Although they look quite different, Legacy and SegWit formats are compatible; Segwit users can send funds to Legacy addresses and vice versa. However, using a Segwit address instead of a Legacy address means that it can hold more and save on transaction fees.
Legacy addresses are seen as ‘insecure’ because unlike SegWit, they don’t support the improved security of more complex Bitcoin transactions. Furthermore, a Legacy address places lower priority on validating scripts, making it more vulnerable to potential hacks.
That said, Legacy addresses are perfectly safe for most people who actively use bitcoin in their everyday lives. As long as people are aware of the differences between Legacy and SegWit addresses and take the necessary precautions, there’s nothing to worry about when using a legacy address.