Regex Tester
Build, test, and debug regular expressions in real-time with match highlighting and instant results — 100% client-side
About What is a Regex Tester?
A Regex Tester (Regular Expression Tester) is a powerful online tool that allows developers to build, debug, and test regular expression patterns in real-time.
Our free regex testing tool supports all standard JavaScript regex flags (global, case-insensitive, multiline) and is perfect for validating email addresses, phone numbers, URLs, and creating custom pattern matching rules.
Everything processes client-side in your browser for complete privacy and security.
Key Features of Regex Tester
Everything you need for professional regex tester
Real-time Matching
See matches highlighted instantly as you type your expression and test string.
Multiline Support
Test patterns against large blocks of text, logs, or code with multiline flag.
Flag Controls
Toggle global (g), case-insensitive (i), and multiline (m) flags easily.
Syntax Error Checking
Get immediate feedback on invalid patterns to debug your regex faster.
Easy Copy & Paste
Copy your final regex pattern to clipboard with a single click.
100% Private
All processing happens in your browser. Your data never leaves your device.
How to Use Regex Tester
Follow these simple steps to get started
Enter Your Regex Pattern
Type your regular expression in the input field. Use special characters like \d, \w for patterns.
Add Test String & Set Flags
Paste your test text and toggle g, i, m flags based on your matching needs.
View Real-time Results
See matches highlighted instantly with count displayed. Copy the regex when ready.
Pro Tips
- Use the global (g) flag to find all matches, not just the first one
- The case-insensitive (i) flag is great for matching text regardless of capitalization
- Enable multiline (m) flag when working with text that has line breaks
- Escape special characters with backslash (\) to match them literally
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Frequently Asked Questions
Everything you need to know about Regex Tester
A regular expression is a sequence of characters that defines a search pattern. It's used to find, match, and manage text for tasks like email validation, phone number formatting, and data extraction.
g (Global) finds all matches, not just the first. i (Case-insensitive) ignores case differences. m (Multiline) allows ^ and $ to match line starts/ends, not just string boundaries.
Enter your regex pattern in the first field, add your test string in the text area, toggle flags as needed, and view real-time highlighted matches in the output area.
Email: /^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$/, Phone: /^\d{3}-\d{3}-\d{4}$/, URL: /^https?:\/\/[^\s]+$/, Digits only: /^\d+$/
Yes! All regex processing happens entirely in your browser using JavaScript. Your text and patterns are never uploaded to our servers or stored anywhere.
This error means your regex has a syntax error. Common causes include unescaped special characters, mismatched parentheses or brackets, and incomplete quantifiers.
Characters with special meaning in regex need backslash escaping: . * + ? [ ] ( ) { } ^ $ | \. For example, to match a literal dot, use \.
Yes, since processing is client-side, you can test large text blocks. However, extremely large inputs with complex regex may slow your browser temporarily.
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