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Free Regex Tester Online
Test regular expressions with live match highlighting, capture groups and replace mode — free, no signup, runs instantly in your browser.
Flags: g=global, i=case-insensitive, m=multiline, s=dotAll
How to use Regex Tester
Enter a pattern
Type your regex between the slashes and set flags (g, i, m, s) on the right.
Add a test string
Matches highlight live as you type. Switch to Replace or Groups to go deeper.
Inspect the results
See match count, run replacements with $1/$2 back-references, and view capture groups.
Frequently Asked Questions
Which regex flavor does this tester use?
This tester uses JavaScript's built-in RegExp engine — the same regex flavor used in Node.js, Chrome DevTools, and all modern browsers. It supports lookahead/lookbehind (ES2018+), named capture groups, and the s (dotAll) flag. PCRE-specific features like (?P<name>) are not supported — use (?<name>) for named groups instead.
How do I use capture groups in the replace?
Use $1, $2, etc. to reference capture groups in the replacement string. For example, pattern (\w+)\s(\w+) with replacement $2, $1 will swap two words. For named groups, use $<name>. Use $& to insert the whole match.
Why use this instead of regex101?
regex101 is great but requires an account to save patterns and is more complex than most developers need. This tester is a clean, fast, no-signup alternative for everyday JavaScript regex testing — match highlighting, replace mode, and group inspection all in one page.