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Last active July 8, 2025 08:24
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Regex cheatsheet
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regex-tips.md

Regex cheatsheet

UK National Insurance Number

^[a-zA-Z]{2}(?:\s*\d\s*){6}[a-zA-Z]?\s*$

HTML: Demote all (second) duplicate H1 tags to H2

Search

((<h1>[^<]*<\/h1>)(.|\s)+?)<h1>([^<]*)<\/h1>

Replace

$1<h2>$4</h2>
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