Regular Expressions 101

.*?any character (except for line terminators), repeated any number of times

Non-Capturing Group(?:(?:[0-9]{2}[/-]){2}[0-9]{4}|[0-9]{4}(?:\h[0-9]{4}){2})

1st Alternative(?:[0-9]{2}[/-]){2}[0-9]{4}

Non-Capturing Group(?:[0-9]{2}[/-]){2}

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

Character Class[0-9]{2}

{2}matches exactly 2 characters from the set below:

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

Character Class[/-]

/the literal / (47₁₀ / 57₈ / 2F₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

Character Class[0-9]{4}

{4}matches exactly 4 characters from the set below:

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

2nd Alternative[0-9]{4}(?:\h[0-9]{4}){2}

Character Class[0-9]{4}

{4}matches exactly 4 characters from the set below:

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

Non-Capturing Group(?:\h[0-9]{4}){2}

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

\hany horizontal whitespace character

Character Class[0-9]{4}

{4}matches exactly 4 characters from the set below:

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

.*any character (except for line terminators), repeated any number of times

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

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Search reference

Regular Expression

.*?(?:(?:[0-9]{2}[/-]){2}[0-9]{4}|[0-9]{4}(?:\h[0-9]{4}){2}).*

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