How to Use
What is a regular expression?
A regular expression (regex) is a pattern that describes a set of strings. It is used for search, validation and text transformation.
How to use it
1. Enter a pattern in the Pattern field.
2. Enter test text in the Test Text area.
3. Watch matches highlight in real time.
4. Toggle flags such as g, i, m, s, u and y.
Common presets
- Email, mobile phone, URL, IPv4 and date patterns
- Chinese ID card, postal code and license plate patterns
- UUID, HTML tag and JSON key patterns
Tips
- Invalid patterns show the browser error message for quick fixes.
- Use the presets panel to start from a tested pattern.
- Combine flags to control global, case-insensitive and multiline matching.
Privacy
Matching runs locally; your text never leaves the browser.