Regex Tester Online
Test Regular Expressions in Real Time
Write and test regex patterns with live match highlighting, capture group inspection, and flag controls. Free, no sign-up, works in your browser.
Open Regex TesterFree forever · No account needed · Works offline
Features
Real-Time Matching
See all regex matches highlighted in your text as you type the pattern. No need to press Enter or click buttons.
Capture Groups
Inspect all capture groups and named groups in the match results panel below the text.
Flag Support
Toggle global, case-insensitive, multiline, dotAll, and Unicode flags with checkboxes.
Match Count
See the total number of matches, their positions, and matched text at a glance.
Browser-Side Only
All processing happens locally. Your regex patterns and test strings never leave your device.
Regex Reference
Built-in regex cheat sheet for quick reference to character classes, anchors, and quantifiers.
Common Regex Patterns
Copy these frequently used patterns to use in our tester or in your code.
^[\w.-]+@[\w.-]+\.[a-zA-Z]{2,}$URL
https?:\/\/[\w\-.]+(\.[a-z]{2,})+IPv4
\b(?:\d{1,3}\.){3}\d{1,3}\bPhone (US)
\(?\d{3}\)?[\s.-]\d{3}[\s.-]\d{4}Date (YYYY-MM-DD)
\d{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[12]\d|3[01])Hex Color
#(?:[0-9a-fA-F]{3}){1,2}\bCommon Use Cases
Email Validation
Write and test regex patterns to validate email addresses, phone numbers, and postal codes in form fields.
Log File Parsing
Build patterns to extract timestamps, error codes, IP addresses, and other structured data from log files.
Data Extraction
Extract specific fields from structured text like CSV, HTML, and API responses using capture groups.
URL Pattern Matching
Test URL routing patterns for web frameworks like Express, Django, and Laravel.
Search & Replace
Test find-and-replace patterns before using them in editors like VS Code, Vim, or code scripts.
Input Sanitization
Validate and sanitize user input on the front-end by testing your validation regex in real time.
Frequently Asked Questions
What is a regex tester?
A regex tester (regular expression tester) is a tool that lets you write a regex pattern and test it against sample text in real time. It highlights all matches, shows capture groups, and helps you debug and refine your patterns.
What regex flavors does this tool support?
The WebToolsBox Regex Tester primarily uses JavaScript regex syntax, which is compatible with many languages. It supports all standard regex features including lookahead, lookbehind, named capture groups, and Unicode character classes.
What regex flags are supported?
The regex tester supports all standard flags: g (global - find all matches), i (case-insensitive), m (multiline - ^ and $ match line boundaries), s (dotAll - dot matches newlines), and u (Unicode mode).
Can I use this regex tester for Python?
Most Python regex patterns work with the JavaScript regex engine since they share similar syntax. Minor differences exist, such as Python using (?P<name>) for named groups while JavaScript uses (?<name>). For production Python code, always test with Python's re module.
Is this regex tester free?
Yes, completely free. No sign-up, no account, no limits. Test as many regex patterns as you need.