Regex Tester
Test JavaScript regular expressions with live match highlighting
Enter a pattern above to start matching
Quick Guide
- Enter a pattern without slashes — e.g.
\d+ - Enable the g flag to find all matches
- Matches are highlighted yellow in the preview below
- Capturing groups are shown per match
Common Regex Examples
Click any example to load it into the tester:
^[^\s@]+@[^\s@]+\.[^\s@]+$
Email address
^[A-Z]{1,2}\d[A-Z\d]? \d[A-Z]{2}$
UK Postcode
^(\d{1,3}\.){3}\d{1,3}$
IPv4 address
\b\d{4}-\d{2}-\d{2}\b
ISO date (YYYY-MM-DD)
https?:\/\/[^\s]+
URL
What is a Regular Expression?
A regular expression (regex) is a sequence of characters that defines a search pattern. They are used in JavaScript, Python, Bash, and most other languages for:
- Validating inputs (emails, postcodes, phone numbers)
- Extracting data from text and log files
- Finding and replacing text patterns
- Parsing structured data formats
Regex Flags Explained
| Flag | Name | Description |
|---|---|---|
| g | Global | Find all matches, not just the first |
| i | Case-insensitive | Match regardless of upper/lower case |
| m | Multiline | ^ and $ match start/end of each line |
| s | DotAll | . matches newline characters too |
| u | Unicode | Enables full Unicode matching |