RegEx Validator & Tester 100% Client-Side • Instant Validation

Test, validate, and debug regular expressions in real time. Inspect match highlights, extract capture groups, test live text substitutions, load pre-built validator patterns, and export polyglot code with zero server uploads.

⚡ Common Validators:

🔍 Regular Expression Pattern

Click flag pills to toggle modifier options

/ /

✅ Valid RegEx • Ready

🧪 Test String & Live Match Highlighting

0 lines, 0 chars

Input Test Text (Editable):

Real-Time Highlighted Matches:

📊 Match Breakdown & Capture Groups

Extracted capture groups and index coordinates

Match #	Span [Start:End]	Capture Identifier	Extracted Value
No matching captures to display.

🔄 String Substitution & Replacement

Supports reference tokens e.g. $& (full match), $1, $2, or custom text

💻 Polyglot Code Snippets

📖 RegEx Quick Reference Cheat Sheet

Fast syntax lookup for common tokens and expressions

Character Classes

Any character except newline .
Any digit [0-9] \d
Non-digit [^0-9] \D
Word character [a-zA-Z0-9_] \w
Non-word character \W
Whitespace (space, tab) \s
Non-whitespace \S

Anchors & Boundaries

Start of string / line ^
End of string / line $
Word boundary \b
Non-word boundary \B
Literal escape character \

Quantifiers

0 or more (greedy) *
1 or more (greedy) +
0 or 1 (optional) ?
Exactly N times {n}
N or more times {n,}
Between N and M times {n,m}
Lazy quantifier +?

Groups & Lookaround

Capturing group (abc)
Non-capturing group (?:abc)
Named capture group (?<id>abc)
Positive lookahead (?=abc)
Negative lookahead (?!abc)
Positive lookbehind (?<=abc)

📘 The Complete Guide to RegEx Validation & Testing

Test and validate regular expressions against real-world sample inputs with instant visual feedback and absolute client-side privacy.

⚡ Real-Time Validation

Instantly highlights matching substrings and extracts capture groups as you type. Syntax errors are caught dynamically, providing instant explanations without browser freezing.

🚩 RegEx Flags Explained

Flags modify matching behavior: g (global) finds all occurrences; i (case-insensitive) matches uppercase and lowercase; m (multiline) binds ^ and $ to each line; and s (dotAll) allows the dot . to cross newlines.

🏷️ Capture Groups & Named Groups

Enclosing patterns in parentheses creates capture groups. Access groups numerically in code (match[1]) or by name (match.groups.name) using named group syntax (?<name>...).

🔄 Live Substitution

Preview text replacement operations live using standard replacement tokens ($& for full match, $1 for capture group 1, or static replacement text).

🛡️ ReDoS Protection

Catastrophic backtracking occurs when poorly bounded quantifiers attempt exponential combinations. Test your patterns safely in client memory to verify linear performance.

🔒 100% Client-Side Privacy

All regular expressions, sensitive sample strings, passwords, and tokens remain strictly inside your browser sandbox. Nothing is transmitted over the network.