Regular Expressions 101

^start of line

Non-Capturing Group(?:(?:1?\d{1,4}|20[0-3]\d\d|204[0-6]\d|2047[0-8])(?:\.\d+)?|20479(?:\.0+)?)

1st Alternative(?:1?\d{1,4}|20[0-3]\d\d|204[0-6]\d|2047[0-8])(?:\.\d+)?

Non-Capturing Group(?:1?\d{1,4}|20[0-3]\d\d|204[0-6]\d|2047[0-8])

1st Alternative1?\d{1,4}

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

\d{1,4}a digit, repeated between 1 and 4 times

2nd Alternative20[0-3]\d\d

20the literal text 20

Character Class[0-3]

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

\da digit

3rd Alternative204[0-6]\d

204the literal text 204

Character Class[0-6]

0-6one character from 0 (48₁₀) to 6 (54₁₀)

\da digit

4th Alternative2047[0-8]

2047the literal text 2047

Character Class[0-8]

0-8one character from 0 (48₁₀) to 8 (56₁₀)

Non-Capturing Group(?:\.\d+)?

?repeats the group contents below at most once:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

\d+a digit, repeated at least once

2nd Alternative20479(?:\.0+)?

20479the literal text 20479

Non-Capturing Group(?:\.0+)?

?repeats the group contents below at most once:

\.the literal . (46₁₀ / 56₈ / 2E₁₆)

0+the literal 0 (48₁₀ / 60₈ / 30₁₆) , 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

^(?:(?:1?\d{1,4}|20[0-3]\d\d|204[0-6]\d|2047[0-8])(?:\.\d+)?|20479(?:\.0+)?)$

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