[SOLVED] RegEx to match Bitcoin addresses?

RegEx to match Bitcoin addresses?

I am trying to come up with a regular expression to match Bitcoin addresses according to these specs:

A Bitcoin address, or simply address, is an identifier of 27-34 alphanumeric characters, beginning with the number 1 or 3 [...]

I figured it would look something like this

/^[13][a-zA-Z0-9]{27,34}/

Thing is, I'm not good with regular expressions and I haven't found a single source to confirm this would not create false negatives.

I've found one online that's ^1[1-9A-Za-z][^OIl]{20,40}, but I don't even know what the [^OIl] part means and it doesn't seem to match the 3 a Bitcoin address could start with.

Solution

[^OIl] matches any character that's not O, I or l. The problems in your regex are:

You don't have a $ at the end, so it'd match any string beginning with a BC address.
You didn't count the first character in your {27,34} - that should be {26,33}

However, as mentioned in a comment, a regex is not a good way to validate a bitcoin address.