Comment by aaronpk

Consider using only the character set in NewBase60 to ensure all your URLs are print-safe and unambiguous. If you follow the NewBase60 algorithm it has built-in error correction (e.g. O is considered the same as 0)

Character set: [0-9A-HJ-NP-Z_a-km-z]

More background: http://ttk.me/w/NewBase60