About this tool
Test a JavaScript regular expression against your text: highlighted matches, positions and capture groups, plus replace and split previews — with a hard time limit.
The pattern runs with the browser’s own regular-expression engine in a separate background task. If it takes longer than the limit (for example because of catastrophic backtracking), the task is stopped and you get a message instead of a frozen page.
Example: \d{4}-\d{2}-\d{2} finds the two dates in “Due 2026-01-31, paid 2026-02-03”.
Syntax is JavaScript (ECMAScript): named groups (?<name>…), lookbehind and \p{…} with the u flag work; PCRE-only features such as possessive quantifiers do not.
Quick steps
- Paste your text or open a file (or press Try an example).
- Choose the options — the result updates as you type.
- Copy the result or download it as a file.
Everything runs in your browser. Nothing you type is sent to 1CLIK.
FAQ
How does the Regex Tester work?
The pattern runs with the browser’s own regular-expression engine in a separate background task. If it takes longer than the limit (for example because of catastrophic backtracking), the task is stopped and you get a message instead of a frozen page.
What should I keep in mind?
Syntax is JavaScript (ECMAScript): named groups (?<name>…), lookbehind and \p{…} with the u flag work; PCRE-only features such as possessive quantifiers do not.
Is my text uploaded or saved?
No. It is processed on your device in a separate background task that is stopped if it takes too long; nothing is stored or sent.