API & Queries · 100% Client-Side Browser Utility

Regex Tester & Regular Expression Debugger

Free online Regex Tester and Regular Expression debugger for JavaScript & TypeScript. Highlight matches in real time, inspect numbered & named capture groups, and test presets for Email, URL, UUID, and IPv4.

About Regex Tester & Regular Expression Debugger

Test regular expressions in real time with match highlighting, capture groups, and common pattern presets. All processing executes locally inside your browser session with zero server uploads or telemetry retention.

Key Developer Workflows & Capabilities — Regex Tester

Test JavaScript / TypeScript ECMAScript regular expressions with live match highlighting
Inspect numbered capture groups ($1, $2) and named capture groups (?<name>...) per match
Toggle RegExp flags (g global, i case-insensitive, m multiline, s dotAll, u unicode)
One-click regex presets for validating Emails, URLs, UUIDs, IPv4 addresses, Dates, and Passwords

Common Developer Searches & Supported Formats

regex tester online · regular expression debugger · javascript regex tester · test regexp online · regex capture group viewer · regex101 alternative · email validation regex

Frequently Asked Questions — Regex Tester & Regular Expression Debugger

What regular expression flavor does this Regex Tester use?

It uses the standard ECMAScript (JavaScript / TypeScript / Node.js) RegExp engine with full support for flags (g, i, m, s, u), positive/negative lookaheads, lookbehinds, and named capture groups.

Can I inspect individual capture groups and character offsets for each match?

Yes. Every match is listed with its exact start/end character index, full match string, numbered capture groups ($1, $2...), and named capture groups.

Does the Regex Tester include ready-to-use validation patterns?

Yes. Use the built-in pattern presets to load battle-tested regular expressions for Email addresses, HTTPS URLs, IPv4 addresses, RFC-4122 UUIDs, ISO dates, and semantic version numbers.

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