Regex Tester

Why use Tabreon for this?

• Matching runs entirely in your browser using JavaScript's native regex engine — nothing you type is sent to a server.
• Supports the standard g, i, m, and s flags together, so you can test exactly the matching behavior your code will use.
• Live match count and highlighting update as you edit the pattern or test string.

How to test a regular expression

1. 1Enter your pattern. Type the regular expression pattern you want to test.
2. 2Set flags. Toggle global (g), case-insensitive (i), multiline (m), and dotAll (s) as needed.
3. 3Enter test text and review matches. Paste the string to test against — matches highlight instantly, with a live count.

What do the regex flags do?

The "g" (global) flag finds every match instead of stopping at the first. "i" (case-insensitive) ignores letter case. "m" (multiline) makes ^ and $ match the start and end of each line rather than just the whole string. "s" (dotAll) makes "." match newline characters too, which it otherwise doesn't. Combining flags changes matching behavior significantly, which is why testing with the exact flags your code uses matters.

How Tabreon handles your data

Matching runs in your browser using JavaScript's native RegExp engine — neither your pattern nor your test string is sent to a server.

Key features

• Live match highlighting as you type
• Support for g, i, m, and s flags in any combination
• Match count and each match's position
• Clear error message for an invalid pattern

Common use cases

• Validating an email or phone number pattern before using it in form validation
• Debugging why a regex in production code isn't matching as expected
• Testing a find-and-replace pattern against sample text before running it on real data

Common mistakes & limitations

• This tests JavaScript's regex engine specifically — patterns using syntax from other regex flavors (PCRE, POSIX) may behave differently here than in another language.