Regular Expressions 101

Explanation

Pro

^start of line

\d{6}a digit, repeated exactly 6 times

Positive Lookahead(?=(\d))

Group 1(\d)

\da digit

Non-Capturing Group(?:\1\d){3}

{3}repeats the group contents below exactly 3 times:

\1the text saved by group 1

\da digit

$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.

25 tokens

^\d{6}(?=(\d))(?:\1\d){3}$

New

502632959793
 - TRUE
125632757773
 - TRUE
475632353773
 - FALSE

502632959793
 - TRUE
125632757773
 - TRUE
475632353773
 - FALSE