Regular Expressions 101

^start of line

Positive Lookahead(?=\d+$)

\d+a digit, repeated at least once

$end of line

\d*?a digit, repeated any number of times

Non-Capturing Group(?:0(?=[1-9])|1(?=[2-9])|2(?=[3-9])|3(?=[4-9])|4(?=[5-9])|5(?=[6-9])|6(?=[7-9])|7(?=[89])|8(?=9)){4}

{4}repeats the group contents below exactly 4 times:

1st Alternative0(?=[1-9])

0the literal 0 (48₁₀ / 60₈ / 30₁₆)

Positive Lookahead(?=[1-9])

Character Class[1-9]

1-9one character from 1 (49₁₀) to 9 (57₁₀)

2nd Alternative1(?=[2-9])

1the literal 1 (49₁₀ / 61₈ / 31₁₆)

Positive Lookahead(?=[2-9])

Character Class[2-9]

2-9one character from 2 (50₁₀) to 9 (57₁₀)

3rd Alternative2(?=[3-9])

2the literal 2 (50₁₀ / 62₈ / 32₁₆)

Positive Lookahead(?=[3-9])

Character Class[3-9]

3-9one character from 3 (51₁₀) to 9 (57₁₀)

4th Alternative3(?=[4-9])

3the literal 3 (51₁₀ / 63₈ / 33₁₆)

Positive Lookahead(?=[4-9])

Character Class[4-9]

4-9one character from 4 (52₁₀) to 9 (57₁₀)

5th Alternative4(?=[5-9])

4the literal 4 (52₁₀ / 64₈ / 34₁₆)

Positive Lookahead(?=[5-9])

Character Class[5-9]

5-9one character from 5 (53₁₀) to 9 (57₁₀)

6th Alternative5(?=[6-9])

5the literal 5 (53₁₀ / 65₈ / 35₁₆)

Positive Lookahead(?=[6-9])

Character Class[6-9]

6-9one character from 6 (54₁₀) to 9 (57₁₀)

7th Alternative6(?=[7-9])

6the literal 6 (54₁₀ / 66₈ / 36₁₆)

Positive Lookahead(?=[7-9])

Character Class[7-9]

7-9one character from 7 (55₁₀) to 9 (57₁₀)

8th Alternative7(?=[89])

7the literal 7 (55₁₀ / 67₈ / 37₁₆)

Positive Lookahead(?=[89])

Character Class[89]

9th Alternative8(?=9)

\d+a digit, repeated at least once

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

Regular Expression

^(?=\d+$)\d*?(?:0(?=[1-9])|1(?=[2-9])|2(?=[3-9])|3(?=[4-9])|4(?=[5-9])|5(?=[6-9])|6(?=[7-9])|7(?=[89])|8(?=9)){4}\d+

New

11111
12345
13456
134356
134567
1345657
1345678
1355678

00001459000
abc12345
9871234444