Regular expression tester
Test JavaScript regular expressions with highlighted matches, capture groups and optional replacement. Files and entered content are not sent to or stored on a server.
How to use
Test JavaScript regular expressions with highlighted matches, capture groups and optional replacement.
Supported formats & limits
Values → Result
Processing stays in this browser. File formats and available memory may limit the result.
Without g, only the first match is returned. Match positions are JavaScript zero-based UTF-16 offsets.
Regular expression tester User guide
Instructions
- Use the visible syntax reference to enter an expression without / delimiters and choose flags.
- Enter test text and optionally a replacement using $1 / $&.
- Run the test and inspect highlights, positions, groups and replaced text.
Example
Input / settings
(\d+) · g · A12 B34
Result / checks
12, 34 with group 1
Please note
- Without g, only the first match is returned. Match positions are JavaScript zero-based UTF-16 offsets.
- A separate worker is stopped after one second. Up to 2,000 matches and 200,000 input characters.