Why did my pattern time out?

Usually nested quantifiers over a long string — something like (a+)+b. The engine explores exponentially many paths. Anchor the pattern or make the inner quantifier lazy.

Regex Tester

Test a pattern against sample text with live highlighting.

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About this tool

Matching runs in a Web Worker with a time budget, so a pattern that backtracks catastrophically stops the worker instead of freezing the page.

Limitations

Uses the JavaScript regex engine. PCRE features such as atomic groups, possessive quantifiers and recursion are not available.
Evaluation is abandoned after a timeout. That is a safeguard, not a verdict on your pattern.

Questions

Why did my pattern time out?: Usually nested quantifiers over a long string — something like (a+)+b. The engine explores exponentially many paths. Anchor the pattern or make the inner quantifier lazy.

Privacy

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