Free Online Regex Tester
Test and debug your regular expressions instantly with our free online regex tester. Whether you are validating form inputs, parsing log files, or extracting data from text, this tool gives you real-time match highlighting, capture group details, and a powerful find-and-replace feature. Everything runs in your browser — no signup, no data stored on servers.
Features
- Real-Time Match Highlighting — See matches highlighted in your test string as you type, with alternating colors for clarity
- Capture Groups — View all capture groups for each match, including named groups
- Regex Flags — Toggle global (g), case-insensitive (i), multiline (m), dotall (s), and unicode (u) flags
- Find & Replace — Replace matches using regex replacement syntax ($1, $2, named groups)
- Common Patterns — Quick-insert patterns for email, phone, URL, IP address, date, and more
- Regex Cheat Sheet — Built-in reference for character classes, quantifiers, anchors, groups, and lookarounds
- Dark & Light Theme — Toggle for comfortable editing in any environment
- 100% Client-Side — Your text and patterns never leave your browser
How to Use
- Enter your regex pattern in the pattern field at the top
- Toggle the desired flags (g, i, m, s, u) using the flag buttons
- Type or paste your test string in the text area below
- Matches are highlighted in real time. Check the Match Results panel for details including capture groups
- To replace, enter a replacement string and click Replace All
Frequently Asked Questions
Is my data safe?
Yes. All regex matching and replacement happens entirely in your browser using JavaScript. No data is sent to any server. Your text never leaves your machine.
Which regex flavor does this tool use?
This tool uses JavaScript's built-in RegExp engine. It supports all modern features including named capture groups, lookbehinds, and the unicode flag. The syntax is compatible with most web and Node.js applications.
What do the flags mean?
g (global) finds all matches, not just the first. i makes the match case-insensitive. m (multiline) makes ^ and $ match line boundaries. s (dotall) makes . match newlines. u (unicode) enables full Unicode matching.
How do I use capture groups in replacement?
Use $1, $2, etc. to reference numbered capture groups, or $<name> for named groups. $& inserts the entire match, and $$ inserts a literal dollar sign.