Regex Tester
Test regular expressions, flags, and matches against text directly in your browser.
What a regular expression is
A regex describes text patterns. It can find numbers, check formats, or extract fragments, but a match does not replace complete contextual validation.
The g, i, and m flags
g finds multiple matches, i ignores letter case, and m changes how ^ and $ work across lines. The s, u, and y flags are also supported.
Limits and expensive expressions
The tester limits patterns to 300 characters, text to 20,000, and results to 1,000. Some expressions can still be expensive due to backtracking; limits reduce risk but do not make every regex safe.
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