Test Regular Expressions with Live Highlighting
Match highlighting, named groups, replace preview, and common pattern shortcuts — all in your browser.
Uses JavaScript's native RegExp engine. All processing happens in your browser.
How to use the regex tester
- Enter your regular expression in the pattern bar at the top.
- Toggle flags (g, i, m, s) using the buttons next to the pattern.
- Paste your test string or use the built-in sample text.
- Matches are highlighted in yellow in real time.
- Optionally enter a replacement string to preview substitutions.
Common regex patterns
- Email:
[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,} - URL:
https?://[^\s]+ - IPv4:
\b(?:\d{1,3}\.){3}\d{1,3}\b - Date (YYYY-MM-DD):
\d{4}-\d{2}-\d{2} - Hex colour:
#(?:[0-9a-fA-F]{3}){1,2}\b
Frequently asked questions
This tool uses JavaScript's native RegExp engine, which supports standard features including character classes, quantifiers, groups, lookaheads, lookbehinds, named capture groups, and Unicode properties.
g (global) finds all matches instead of stopping at the first. i (case-insensitive) makes the match ignore letter case. m (multiline) makes ^ and $ match the start and end of each line. s (dotAll) makes the dot . match newline characters too.
Use the (?<name>...) syntax. For example, (?<year>\d{4})-(?<month>\d{2}) captures year and month as named groups. The tool displays captured group values in the Named Groups panel.
Enter a replacement string in the Replace field. Use $1, $2 etc. to insert numbered capture groups, or $<name> for named groups. The replaced result is shown live below the input.
Greedy quantifiers (*, +, ?) match as many characters as possible. Use lazy versions (*?, +?, ??) to match as few as possible. Use anchors (^ and $) and word boundaries (\b) to be more precise.
Yes. The regex engine runs entirely in your browser using JavaScript. Your test string is never sent to any server.
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