Regex Tester (Matches, Groups, and Replacement Preview)
Need to run a regex test quickly? Paste and verify immediately with this regex tester.
See highlighted matches, capture groups, and replacement output in one screen.
Your input is processed locally in the browser and is not sent to a server.
How to use
- Enter a pattern and choose the flags you need (g/i/m).
- Paste source text. If auto-run is ON, results update immediately.
- Use the match list to inspect locations and jump to each match.
- Use Groups and Replacement tabs to verify captures and replacement output.
Examples
Email extraction
Input: Text containing email addresses
Output: Highlighted matches and start/end positions
key=value replacement
Input: Multi-line key=value text
Output: Replacement output using $1 and $2
Log line filter
Input: Log text with INFO / WARN / ERROR
Output: Line-based matching with m flag
Replacement Cheat Sheet
- $1, $2 ... : capture group references
- $& : whole match
- $` : before match / $' : after match
Note
- This tool evaluates patterns using JavaScript (ECMAScript) regular expressions.
- Some PCRE features (such as atomic groups) are not available.
- Even JavaScript features can vary by runtime environment.
- Results are not guaranteed to be identical to PCRE.
FAQ
What are g/i/m flags?
Use checkboxes to toggle them. (g=global, i=ignore case, m=multiline)
Can I test replacement too?
Yes. Enter a replacement string and check the Replacement tab. Group references like $1 are supported.
How is this different from PCRE?
This tool uses JavaScript regular expressions. Because of spec differences, the same pattern may produce different results from PCRE.