Regular Expressions 101

Group 1(\d{4})

\d{4}a digit, repeated exactly 4 times

Group 2(-?)

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

Group 3(\d{4})

\d{4}a digit, repeated exactly 4 times

Group 4(\2\d{4}){2}

{2}repeats the group contents below exactly 2 times:

\2the text saved by group 2

\d{4}a digit, repeated exactly 4 times

Global pattern flags

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

Detailed match information will be displayed here automatically.

25 tokens

Regular Expression

(\d{4})(-?)(\d{4})(\2\d{4}){2}

New

5123-4567-8912-3456
61234-567-8912-3456
4123356789123456
5133-3367-8912-3456