[est]

Ha, trying to paste "regex filter numbers divisible by 3" and the page froze to death https://stackoverflow.com/q/10992279/41948

    ^(?:[0369]+|[147](?:[0369]*[147][0369]*[258])*(?:[0369]*[258]|[0369]*[147][0369]*[147])|[258](?:[0369]*[258][0369]*[147])*(?:[0369]*[147]|[0369]*[258][0369]*[258]))+$

    ^([0369]|[147][0369]*[258]|(([258]|[147][0369]*[147])([0369]|[258][0369]*[147])*([147]|[258][0369]\*[258])))+$

I wonder if there's a shortest one.

[abareplace]

The web page hangs on the regular expressions that produce a DFA with a lot of states. For example, these ones:

(ab+c+)+

(abc){100}

a.*quick brown fox jumps over the lazy dog

[zamadatix]

The page says it doesn't support anchors anyway.