How do I test a regular expression?

Enter your regex pattern in the pattern field, select any flags (g, i, m, s), and type or paste your test string below. Matches are highlighted in the text and listed below with their index and capture groups.

What regex flags are supported?

The tester supports the four most common JavaScript flags: g (global — find all matches), i (case-insensitive), m (multiline — ^ and $ match line boundaries), and s (dotAll — dot matches newlines).

Is the regex tester free?

Yes, completely free. Regex testing runs entirely in your browser using the built-in JavaScript RegExp engine — no data is sent to any server, and no signup is required.

Regex Tester

Test and debug regular expressions instantly online. Highlights matches, shows capture groups, and supports all JavaScript regex flags (g, i, m, s). Free regex tester — no signup required.

Pattern/g

Test String

Related Tools

JWT Decoder

Decode JWT tokens instantly. Inspect header and payload client-side — your token never leaves the browser.

Unix Timestamp

Convert Unix timestamps to UTC, local time, and ISO 8601 instantly. Auto-detects seconds vs milliseconds.

Base Converter

Convert numbers between decimal, hex, binary, and octal instantly. Free and runs in your browser.

Supported Flags

g (global) — find all matches in the string, not just the first
i (case-insensitive) — match upper and lower case letters
m (multiline) — ^ and $ match the start/end of each line
s (dotAll) — dot . matches newline characters

Quick Reference

.Any character

\dDigit (0–9)

\wWord char

\sWhitespace

^Start of string

$End of string

*0 or more

+1 or more

?0 or 1

(...)Capture group

[abc]Character class

[^abc]Negated class