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How to Use Regex Tester: Complete Guide (2026)
Learn how to use regex tester free online — no signup, no download. Follow our step-by-step guide below.
What is Regex Tester?
Test regular expressions against sample text with real-time matching highlights. Supports JavaScript, Python, and PCRE regex flavors. Features match groups display, replace preview, and common pattern library. Essential for form validation, data extraction, and text processing.
- 100% browser-based — no data uploaded to servers
- Free to use — no signup required
- Instant results — no waiting
- Works on all devices — mobile, tablet, desktop
How to Use Regex Tester: Step-by-Step
- 1
Enter a regex pattern
Type your regular expression pattern (e.g., ^[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,}$).
- 2
Add test string
Paste or type the text you want to test against.
- 3
View matches
Matching portions are highlighted. Match groups are displayed below.
- 4
Test replace
Optionally enter a replacement string to preview the result of regex replace.
Common Use Cases
Form validation
Test email, phone, and password validation regex patterns before deploying.
Data extraction
Build regex patterns to extract URLs, dates, or structured data from text.
Log analysis
Create regex patterns to parse and filter server log files.
FAQ About Regex Tester
Which regex flavor is used?
By default, JavaScript regex (ECMAScript). You can switch to Python or PCRE mode for advanced features like lookbehind.
What does the 'g' flag do?
The 'g' (global) flag finds ALL matches, not just the first one.
Why is my regex not matching?
Common issues: forgetting to escape special chars (., *, +), or using greedy quantifiers (*) when you want lazy (*?). Check the flags too.
Ready to Try Regex Tester?
No signup. No download. 100% free.