Regex Tester
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About Regex Tester
Regex Tester lets you write, test, and debug regular expressions against sample text in real time. It visually highlights all matches, displays capture groups, and explains each part of your pattern so you can build complex regex with confidence. This tool is invaluable for developers, data engineers, and anyone who needs to parse, validate, or extract patterns from text.
Key Features
- Real-time match highlighting as you type your regex pattern
- Displays all capture groups, named groups, and their matched values
- Supports common regex flags including global, case-insensitive, multiline, and dotall
- Provides a match information panel showing index, length, and group details for each match
- Includes a quick-reference cheat sheet for common regex syntax
- Allows testing against multiple lines of sample text simultaneously
How to Use Regex Tester
- 1
Enter your regular expression
Type or paste your regex pattern into the pattern input field. The tool accepts standard JavaScript regex syntax.
- 2
Set your flags
Toggle flags like global (g), case-insensitive (i), or multiline (m) depending on how you want the pattern to behave.
- 3
Provide test strings
Paste the sample text you want to match against in the test string area. You can include multiple lines.
- 4
Review highlighted matches
Matching portions of the text are highlighted instantly. Each capture group is shown in a distinct color for easy identification.
- 5
Inspect match details
Click on any match to see its index, full match value, and the contents of each capture group in the details panel.
Common Use Cases
Form Input Validation
Build and test regex patterns for validating email addresses, phone numbers, postal codes, and other user input formats before implementing them in your application.
Log Parsing
Craft regular expressions to extract timestamps, error codes, IP addresses, and other structured data from server or application log files.
Data Extraction and Scraping
Develop patterns to pull specific information (prices, dates, URLs) from HTML content or raw text during web scraping or ETL pipelines.
Search and Replace in Code
Test complex find-and-replace regex patterns before running them across your codebase in an IDE to avoid unintended modifications.
Why Use Our Regex Tester
Skip the tedious write-run-check cycle by testing regex patterns with instant visual feedback as you type. The capture group breakdown and match detail panel go beyond simple highlighting, giving you the debugging depth that most online regex tools lack. No account needed and no data leaves your browser, so you can test patterns against production log samples worry-free.
Test Against Production Logs Safely
Regex testing often involves pasting real log data containing IP addresses, usernames, session IDs, and error traces. This tool runs entirely in your browser, so sensitive production samples never reach an external server. You can debug patterns against real-world data without any privacy risk.
Learn More
Frequently Asked Questions
Which regex flavor does this tool use?
Can I test regex with lookaheads and lookbehinds?
Why does my regex match more than I expected?
Last updated: April 6, 2026