Regular Expressions 101

^start of line

Group 1((1?[0-9]{0,4})|((20(([0-3][0-9]{0,2})|(4[0-7][0-9])))))

1st Alternative(1?[0-9]{0,4})

Group 2(1?[0-9]{0,4})

1?optionally matches the literal 1 (49₁₀ / 61₈ / 31₁₆)

Character Class[0-9]{0,4}

{0,4}matches between 0 and 4 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

2nd Alternative((20(([0-3][0-9]{0,2})|(4[0-7][0-9]))))

Group 3((20(([0-3][0-9]{0,2})|(4[0-7][0-9]))))

Group 4(20(([0-3][0-9]{0,2})|(4[0-7][0-9])))

20the literal text 20

Group 5(([0-3][0-9]{0,2})|(4[0-7][0-9]))

1st Alternative([0-3][0-9]{0,2})

Group 6([0-3][0-9]{0,2})

Character Class[0-3]

0-3one character from 0 (48₁₀) to 3 (51₁₀)

Character Class[0-9]{0,2}

{0,2}matches between 0 and 2 characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

2nd Alternative(4[0-7][0-9])

Group 7(4[0-7][0-9])

4the literal 4 (52₁₀ / 64₈ / 34₁₆)

Character Class[0-7]

0-7one character from 0 (48₁₀) to 7 (55₁₀)

Character Class[0-9]

0-9one character from 0 (48₁₀) to 9 (57₁₀)

$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

^((1?[0-9]{0,4})|((20(([0-3][0-9]{0,2})|(4[0-7][0-9])))))$

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