Why base-58 instead of standard base-64 encoding?

• Don't want 0OIl characters that look the same in some fonts and could be used to create visually identical looking account numbers.
• A string with non-alphanumeric characters is not as easily accepted as an account number.
• E-mail usually won't line-break if there's no punctuation to break at.
• Double-clicking selects the whole number as one word if it's all alphanumeric.

Features of Base58Check

• An arbitrarily sized payload

• A set of 58 alphanumeric symbols consisting of easily distinguished uppercase and lowercase letters (0OIl are not used)

• One byte of version/application information. Bitcoin addresses use 0x00 for this byte (future ones may use 0x05).

• Four bytes (32 bits) of SHA256-based error checking code. This code can be used to automatically detect and possibly correct typographical errors.
• An extra step for preservation of leading zeroes in the data