<p>I think I found the one with the longest firstbits
<a href="http://blockchain.info/fb/1234567891234567891234567891w" rel="nofollow">http://blockchain.info/fb/1234567891234567891234567891w</a></p>

CC BY-SA 3.0
2013-08-02T00:31:08.940Z
"Sorry this is is not a valid bitcoin address"
Michael Hampton
CC BY-SA 3.0
2013-06-01T22:23:16.320Z
2013-06-01T22:23:16.320Z
lurf jurv
<p>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.</p>

CC BY-SA 3.0
2013-05-29T15:20:24.347Z
No easy way to find [the shortest](http://bitcoin.stackexchange.com/questions/7466/how-to-find-the-shortest-unused-firstbits), so it's not clear why you expect there was an easy way to find the longest, instead.
o0'.
CC BY-SA 3.0
2013-05-29T16:07:48.883Z
@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
CC BY-SA 3.0
2013-05-30T13:02:06.367Z
@NickODell: Unless the longest firstbits is already so long that finding a longer one will be computationally prohibitive.
Meni Rosenfeld
CC BY-SA 3.0
2013-06-01T18:53:46.973Z
Finding the shortest one unused is rather different than finding the longest one used, IMO.
lurf jurv
CC BY-SA 4.0
2020-08-11T13:05:44.507Z
related: https://bitcoin.stackexchange.com/q/3730/5406
Murch
<vanitygen><firstbits>
What is the longest firstbits?
lurf jurv
# What is the longest firstbits?

(Asked by: username_0 on 2013-05-29)

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.

**Tags:** vanitygen, firstbits

> **Comments:**
> **username_1**: No easy way to find [the shortest](http://bitcoin.stackexchange.com/questions/7466/how-to-find-the-shortest-unused-firstbits), so it's not clear why you expect there was an easy way to find the longest, instead.  
> **username_2**: @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.  
> **username_3**: @username_2: Unless the longest firstbits is already so long that finding a longer one will be computationally prohibitive.  
> **username_0**: Finding the shortest one unused is rather different than finding the longest one used, IMO.  
> **username_4**: related: https://bitcoin.stackexchange.com/q/3730/5406  

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## 1 answers

### Answer by username_0 on 2013-06-01. Score: 0

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

> **Comments:**
> **username_5**: "Sorry this is is not a valid bitcoin address"  

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