Why Your Regex Matches Too Much

Find out why a regex matches too much, such as greedy .*, with a runnable case.

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Regular expression
Reference

Regex quick reference

^ · $
Start/end; m = lines.
[abc] · \d
Listed character / digit.
* · + · ?
Zero or more, one or more, optional.
(...)
Capture a numbered group.
(?<name>...)
Named capture.
(?=...)
Ahead; lookbehind varies.
i · m · s
Ignore case / line anchors / dot-newline.
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the RegExp of this browser (version not pinned)

Not available in JavaScript · This browser: x · ignore pattern whitespace; a · ASCII-only classes; U · lazy by default; J · duplicate names. u and v cannot be combined.

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Verified Fixture FX-G02

What it does

A regex that matches too much usually has a greedy .* that runs past the end you intended.

How to use it

  1. Load the failing case and see the single long match.
  2. Replace .* with a class that cannot cross the delimiter.
  3. Compare the corrected matches.

Verified example

As written

Text "<b>one</b> <i>two</i>"

JavaScript · This browser
<.*>

Result: "<b>one</b> <i>two</i>"

Corrected

Text "<b>one</b> <i>two</i>"

JavaScript · This browser
<[^>]*>

Result: "<b>", "</b>", "<i>", "</i>"

Recorded by running fixture FX-G02 on : rp.js@1 on Node v24.21.0 (V8), v24.21.0, CPython 3.14.2 (Pyodide 314.0.7), PCRE2 10.48, go1.27.1. JavaScript results come from the rp.js@1 core on Node’s V8; your browser runs the same core.

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