What is the longest used firstbits? How could I find out? I think it would be two vanity addresses with the same prefix, yes? Anything longer than about seven characters for a firstbits would require a lot of computation.

  • No easy way to find the shortest, so it's not clear why you expect there was an easy way to find the longest, instead.
    – o0'.
    Commented May 29, 2013 at 15:20
  • @Lohoris The largest problem is that if you say "the longest firstbits is 1aaaaaaaaaaa" then somebody with vanitygen will just try to make two vanity addresses that have more characters in common.
    – Nick ODell
    Commented May 29, 2013 at 16:07
  • @NickODell: Unless the longest firstbits is already so long that finding a longer one will be computationally prohibitive. Commented May 30, 2013 at 13:02
  • Finding the shortest one unused is rather different than finding the longest one used, IMO.
    – lurf jurv
    Commented Jun 1, 2013 at 18:53
  • 1
    It is valid (see uncaptcha.net/bitcoin.php ), but I think nobody has the private key... Chance to choice valid address is 1 : 4 billions which is no computational problem...
    – user8674
    Commented Nov 11, 2013 at 8:13

1 Answer 1


I think I found the one with the longest firstbits http://blockchain.info/fb/1234567891234567891234567891w

  • 1
    "Sorry this is is not a valid bitcoin address" Commented Aug 2, 2013 at 0:31

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.