Regex Tester Online | Real-Time Matching, Capture Groups, Debug - {{YEAR}}

What is a Regex Tester? Complete Guide

A regex tester is an essential debugging tool for testing and validating regular expressions (regex patterns) against sample text in real-time. Our 2026 regex tester goes beyond basic tools with real-time pattern matching, capture groups display, match position indexing, all 6 JavaScript regex flags (global, case-insensitive, multiline, dotAll, unicode, sticky), common patterns library for email, URL, phone, IPv4, dates, and hex colors, and comprehensive error validation. Whether you are validating email addresses, extracting data from logs, parsing URLs, searching text, or cleaning datasets, our tester provides instant feedback with match highlighting, group extraction, and detailed error messages. Unlike server-based testers, our tool processes your patterns entirely in your browser ensuring your sensitive regex patterns and test data remain completely private.

How to Use Our Regex Tester

Enter your regular expression pattern in the "Regular Expression" input field
Select regex flags you need: global (g), case-insensitive (i), multiline (m), etc.
Paste or type your test text in the "Test Text" textarea to match against
Click "Test Pattern" to execute the regex and see all matches instantly
Review matches displayed below showing match text, position index, and captured groups
Use "Quick Patterns" to load common regex patterns (email, URL, phone) for learning
Copy the working regex pattern to clipboard for use in your code
Adjust flags or pattern and re-test until you get desired matching behavior

Key Features & Benefits

Real-Time Pattern Testing

Test regex patterns instantly and see all matches with highlighted results. Know immediately if your pattern works before using in production code.

All Regex Flags

Support for all 6 JavaScript regex flags: global (g), case-insensitive (i), multiline (m), dotAll (s), unicode (u), and sticky (y).

Capture Groups Display

View captured groups from each match with clear labeling. Essential for extraction patterns and replacement operations.

Match Position & Index

See exact character position of each match in your text. Helpful for debugging position-specific patterns or range extraction.

Common Patterns Library

Quick access to pre-built patterns for email, URL, phone, IPv4, date (YYYY-MM-DD), and hex color codes. Learn from examples.

Error Validation

Clear error messages for invalid regex syntax. Know exactly what is wrong with your pattern instead of cryptic runtime errors.

Common Use Cases

Input Validation

Test regex patterns for form validation: email addresses, phone numbers, credit cards, zip codes, usernames. Ensure patterns catch all valid cases and reject invalid input.

Log File Parsing

Extract specific data from log files: timestamps, error codes, IP addresses, user IDs. Test extraction patterns against sample logs before processing millions of lines.

Data Cleaning

Test patterns for removing unwanted characters, standardizing formats, extracting structured data from messy text, or replacing patterns in bulk text processing.

URL Routing & Matching

Test route patterns for web frameworks, API endpoints, or URL rewriting rules. Ensure patterns match intended paths and capture correct parameters.

Search & Replace

Test find-and-replace patterns before running on large codebases or documents. Preview matches and capture groups for replacement strings.

Learning Regular Expressions

Students and developers learning regex can experiment with patterns, see immediate results, use common pattern examples, and understand how flags affect matching.

Why Choose Our Regex Tester

✓Instant Testing: See matches immediately with no delays. Test and refine patterns in seconds.
✓All Flags Supported: Unlike basic testers, we support all 6 JavaScript regex flags for complete testing.
✓Match Details: View match text, index position, and capture groups for every match - essential for debugging.
✓Common Patterns: Pre-built patterns for email, URL, phone, and more. Learn by example and adapt to your needs.
✓Privacy Protected: Client-side processing means your regex patterns and test data never leave your browser.
✓100% Free: Unlimited pattern testing without registration, API limits, or premium features.
✓Error Messages: Clear validation errors help you fix broken patterns quickly instead of crashing your code.
✓Multiple Matches: Global flag shows all matches, not just the first. See complete matching behavior.
✓Group Extraction: View captured groups essential for data extraction and replacement patterns.
✓Developer Friendly: Built for developers with clean output, proper JavaScript regex support, and no quirks.

Regex Tester Comparison - How We Compare to Competitors

Feature	10xTools Regex Tester	Regex101	Regexr	RegExPal	Debuggex	RegexOne
Price (Free Forever)	✅ 100% Free	✅ Free	✅ Free	✅ Free	❌ Freemium	✅ Free
All Regex Flags	✅ All 6 Flags	✅ All Flags	✅ All Flags	❌ Limited	✅ All Flags	❌ Limited
Capture Groups	✅ Full Support	✅ Full Support	✅ Full Support	✅ Full Support	✅ Full Support	❌ Not Available
Common Patterns	✅ 6 Patterns	✅ Library	❌ Not Available	❌ Not Available	❌ Not Available	✅ Lessons Only
Real-Time Matching	✅ Instant	✅ Instant	✅ Instant	✅ Instant	✅ Instant	✅ Instant
Match Position	✅ Shown	✅ Shown	✅ Shown	❌ Not Shown	✅ Shown	❌ Not Shown
Error Validation	✅ Detailed	✅ Detailed	✅ Detailed	❌ Basic	✅ Detailed	❌ Basic
Privacy (Client-Side)	✅ 100% Private	❌ Server Upload	❌ Server Upload	❌ Server Upload	❌ Server Upload	❌ Server Upload
No Registration	✅ No Signup	❌ Signup Required	❌ Signup Required	✅ No Signup	❌ Signup Required	✅ No Signup
JavaScript Regex	✅ Full Support	✅ Full Support	✅ Full Support	✅ Full Support	✅ Full Support	✅ Full Support

✅ = Feature Available | ❌ = Not Available or Limited

Frequently Asked Questions

What regex flavor does this tester use?

This tester uses JavaScript regex (ECMAScript) flavor. Syntax may differ slightly from Python (re), PHP (PCRE), or other languages. Test patterns in the environment where you will use them.

What is the difference between regex flags?

Global (g) finds all matches instead of stopping at first. Case-insensitive (i) ignores upper/lowercase. Multiline (m) makes ^ and $ match line starts/ends. DotAll (s) makes . match newlines. Unicode (u) enables Unicode matching. Sticky (y) matches from lastIndex only.

Why does my pattern work here but not in my code?

Different programming languages have different regex flavors with varying syntax. JavaScript regex (used here) differs from Python, Java, PHP, etc. Also check if you need to escape backslashes differently in strings.

How do I escape special characters in regex?

Use backslash \ before special characters: . * + ? ^ $ { } [ ] ( ) | \. For example: \. matches literal dot, \* matches literal asterisk. In code strings, you may need double backslash: \\.

What are capture groups and how do I use them?

Capture groups are patterns wrapped in parentheses ( ). They extract matched portions for reuse in replacements or data extraction. For example: (\d{3})-(\d{3})-(\d{4}) captures phone number parts separately.

Why is my regex slow or timing out?

Catastrophic backtracking can make regex extremely slow. Patterns like (a+)+ or (a*)*b on certain inputs cause exponential complexity. Avoid nested quantifiers and be specific with patterns.

Is my regex pattern safe when using this tester?

Yes! All pattern testing happens entirely in your browser. Nothing is sent to servers or stored. You can verify in browser DevTools Network tab. Safe for proprietary patterns and sensitive test data.

Advanced Regex Tester

Regex Pattern

Try These Tools Too

PDF Merge

PDF Split

PDF Organize

Everything You Need to Know