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Developer Tool
Regex Tester
Test regular expressions in real time. See matches highlighted, capture groups extracted, and positions displayed — all in your browser.
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Common Patterns
Match Preview
Quick Reference
Patterns like these do real work beyond validation. We built a deprecation scanner that is, at bottom, regex over source lines — it walks a repository looking for pinned model names and pmpt_ / eval_ prefixes, and the write-up is candid about where that approach breaks: a reference split across two lines, or an ID assembled from string fragments at runtime, is invisible to it. Testing the pattern here first is how you find out which of those blind spots you actually have.
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Any character except newline
\d
Digit [0-9]
\D
Non-digit
\w
Word char [a-zA-Z0-9_]
\W
Non-word character
\s
Whitespace
\S
Non-whitespace
^
Start of string/line
$
End of string/line
*
Zero or more (greedy)
+
One or more (greedy)
?
Zero or one (optional)
{n,m}
Between n and m times
[abc]
Character class
[^abc]
Negated character class
(abc)
Capture group
(?:…)
Non-capturing group
(?<n>…)
Named capture group
a|b
Alternation (a or b)
\b
Word boundary
(?=…)
Lookahead (positive)
(?!…)
Lookahead (negative)
(?<=…)
Lookbehind (positive)
(?<!…)
Lookbehind (negative)
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