Developer utility

Regex Live Tester and Cheat Sheet

Build JavaScript regular expressions, highlight matches, inspect capture groups, and preview replacements without sending text to a server.

Expression tester

Uses the browser JavaScript RegExp engine.

No uploads

Pattern

/ /g

Sample text 0 chars

Replacement preview 0 chars

Regex compiled.

Matches are highlighted in source order.

0 matches

Capture groups are listed as JSON arrays or named objects.

Limit 100

#	Index	Match	Groups

The global flag finds repeated matches. Without it, JavaScript returns only the first match from the input.

Parentheses capture submatches for extraction and replacement. Named groups make larger expressions easier to read.

JavaScript replacements can use tokens like $& for the full match, $1 for a capture, and $<name> for a named capture.

Usage guide

It compiles JavaScript regular expressions, highlights matches, lists indexes and capture groups, and previews replacement output.

Edit the pattern, toggle flags, paste sample text, and use named groups to confirm exactly what your expression captures.

Use it for log parsing, form validation, search patterns, replacement rules, or learning how anchors, groups, and quantifiers behave.