How to use it
Enter a pattern, choose flags, and paste the text to test. Test uses the JavaScript RegExp engine in your browser. An invalid pattern shows the engine message. Global search stops after 500 matches so a pattern cannot lock the page by returning empty matches forever.
Example
With the global flag, both addresses are listed. The pattern is not applied on the server.
Input
\b\w+@\w+\.\w+\b
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Write to ada@example.com or grace@example.org today.Result
Match 1 at 9: ada@example.com
Match 2 at 29: grace@example.orgHow it works
Flags are the standard JavaScript set: g, i, m, s, and u. The result lists each match, its index, and captured groups. This is not PCRE and not the Java engine.
Common errors
- Invalid regular expression The pattern has an unclosed group, a bad escape, or a flag this browser rejects. The message comes from JavaScript.
- A pattern worked in another language Lookaheads and escapes differ. Treat this page as the JavaScript result only.
- The page stopped listing matches Global mode keeps the first 500 matches.
Limitations
Catastrophic backtracking can still make a pattern slow. Keep test text under 200,000 characters and avoid nested quantifiers on untrusted patterns. The pattern is not sent to the server.
Privacy
The text you paste is processed in your browser. PepsTools does not receive it, store it, or send it to another service.
Questions
Which engine is this?
The regular expression engine built into your browser, exposed as JavaScript RegExp.