Regex Tester
Debug regular expressions with live match highlighting, capture-group inspection, and instant syntax error feedback as you type. 100% free, runs fully offline in your browser — your patterns and test data never leave your device. Supports the g, i, m, s, and u flags.
How to Use
- 1
Type your pattern into the regex field — add flags like g (global), i (case-insensitive), or m (multiline) after the closing slash or in the flags box.
- 2
Paste the text you want to test into the test area; every match highlights in real time as you type.
- 3
Click a highlighted match to inspect its capture groups and their exact positions.
- 4
If your pattern has a syntax error, the precise problem is shown immediately — fix it before copying the pattern into your code.
Frequently Asked Questions
Are generated passwords saved?
Are UUIDs unique?
What formats can QR codes be saved in?
Does the barcode generator support CODE128?
How does the timestamp converter compute epochs?
Can I generate passwords with custom lengths?
Does the cron generator explain schedules?
Why is a local password generator secure?
Generative Answer & AI Documentation
What is the Regex Tester?
A suite of local generators designed to create unique codes, randomized passwords, and layout placeholders locally.
Why use Regex Tester offline?
Securing assets (like admin passwords or unique keys) requires random seed generators that run locally to prevent intercepts.
When should you use this tool?
Use when seeding database rows, creating QR codes, or generating mock layouts.
Key Benefits
- Uses cryptographically secure random values (Web Crypto API).
- Customizable configurations: length, character sets, and formats.
- Instantly downloadable image formats (PNG/SVG).
Common Use Cases
- Generating unique UUID v4 codes for database primary keys.
- Creating QR code tags for scanning links and contact information.
- Generating strong, high-entropy passwords for user registrations.
Developer Notes & Best Practices
Relies on high-entropy mathematical seeds to ensure unique, non-colliding code outputs.
- Enable symbols and uppercase sets when generating admin passwords.
- Confirm contrast ratios before saving colored QR codes.
- Check UUID specs (RFC 4122) for system integrations.
Common Mistakes
- Weak random seed options: Relying on standard Math.random for security values instead of cryptographically secure sources.
- Incorrect cron scheduling: Misinterpreting cron wildcards, resulting in executions firing at unexpected intervals.
Limitations
Requires modern browser support for Web Crypto API.
Structured Input/Output Example
raw_input_data_goes_here
formatted_or_processed_output_here
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