Which regex flavor is supported?

JavaScript regex (ECMAScript 2022). Flags g, i, m, s, u, y are all supported. Lookbehinds and named groups work.

Does it support PCRE or POSIX?

No. For PCRE (Perl) or POSIX regex, use a server-side tester. Most ECMAScript regex translates directly to PCRE.

No. Everything runs in your browser — neither the pattern nor the test string is sent anywhere.

Live as you type, with yellow highlight and a match count. The global flag is always added internally so you see all matches.

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Which regex flavor is supported?: JavaScript regex (ECMAScript 2022). Flags g, i, m, s, u, y are all supported. Lookbehinds and named groups work.
Does it support PCRE or POSIX?: No. For PCRE (Perl) or POSIX regex, use a server-side tester. Most ECMAScript regex translates directly to PCRE.
Is the test string stored?: No. Everything runs in your browser — neither the pattern nor the test string is sent anywhere.
How are matches highlighted?: Live as you type, with yellow highlight and a match count. The global flag is always added internally so you see all matches.