Regex Tester

About Regex Tester

Last updated: May 2026

OptiPix Regex Tester is a full-featured regular expression playground that runs entirely in your browser. Paste or type your regex pattern and test string — matches highlight instantly with alternating colors so you can see boundaries clearly. Every capture group (numbered and named) is listed per match with index ranges. Switch to Replace mode to test substitution patterns with $1, $2, and named back-references. The built-in explanation panel parses your regex token-by-token and translates it into plain English. A collapsible cheatsheet covers character classes, quantifiers, anchors, groups, and lookarounds, and you can click any item to insert it at your cursor. The Common Patterns library loads battle-tested regexes for email, URL, phone, IP, date, hex color, username, and password validation with one click. Catastrophic backtracking protection aborts patterns that take too long. Uses JavaScript's native RegExp engine with full flag support (g, i, m, s, u, y). No accounts, no network calls — your data stays on your device.

How It Works

Constructs a JavaScript RegExp from your pattern and flags, runs matchAll() on the test string, and highlights results in real-time.

Use Cases

• •Debug regex patterns before using in code
• •Validate email/URL/phone patterns
• •Learn regex with explanations
• •Test find-and-replace patterns
• •Extract data with capture groups

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