Regex tester
Tests a regular expression against sample text, run in a background worker with a time budget so a runaway pattern can never freeze this page.
1 · Pattern
2 · Test text
Matching runs in a Web Worker with a time budget - a pattern that runs too long is terminated and flagged as a potential catastrophic-backtracking risk. This is a runtime safeguard, not proof any given pattern is ReDoS-safe. Nothing is sent to a server.
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What this does
Runs your pattern against test text with match highlighting, capture groups, match index, and an optional replace preview, plus a few common example patterns to start from.
Cannot freeze the page
Matching runs in a Web Worker - a separate thread from the page itself - under a fixed time budget. A pattern that does not finish in time is terminated and flagged as a potential catastrophic-backtracking risk. This is a runtime safeguard against a genuinely bad experience, not a proof that any given pattern is provably safe from ReDoS - a pattern that finishes quickly on today's test text could still behave differently on other input.
Privacy
Matched entirely in your browser - nothing is sent to a server.
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