Regular Expressions 101

^start of line

Negative Lookahead(?!.*(\w)\1{3,})

.*any character (except for line terminators), repeated any number of times

Group 1(\w)

\wany word character

\1{3,}the text saved by group 1, repeated at least 3 times

.+any character (except for line terminators), repeated at least once

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

Search reference

Regular Expression

^(?!.*(\w)\1{3,}).+$

New

JHMCU26809C211501 - good
JHMGD18508S219366 - good
JHMCU268091111111 - bad
12345678901234567 - good
ASD1111111ASD2313 - bad
ASDIIIIIIIASDASD2 - bad
IIIIIIIADS1EE2345 - bad