🔎 Regex Tester — Live Match, Groups & Replace
Toolio's Regex Tester is a free, browser-only tool that tests regular expressions instantly — no file uploads, no account required, and fully usable offline.
Regex Pattern
Flags
Test String
Capture Groups (first match)
Replace
About
Enter a regex pattern and a test string to see every match highlighted in real time. Capture groups from the first match are listed with their $1, $2 … references, and the replace preview shows how your substitution string transforms the input. Flags — g, i, m, s, u — are toggled with checkboxes so you never have to remember the syntax. Because everything runs in your browser with no server involved, your patterns and text stay completely private.
How to use
- Type your regular expression into the Pattern field.
- Check the flags you need (g for global, i for case-insensitive, m for multiline, etc.).
- Paste or type your test string in the Test String area — matches highlight immediately.
- Check the Capture Groups panel to inspect $1, $2 … values from the first match.
- Enter a replacement string in the Replace field to preview the result, then copy it.
FAQ
- Is this regex tester free?
- Yes, completely free — no account, no subscription, no usage limits.
- Does it upload my pattern or text to a server?
- No. Everything runs locally in your browser using the JavaScript RegExp engine. Nothing is ever sent to any server.
- Does it work offline?
- Yes. Once the page is loaded, you can disconnect from the internet and it continues to work. The tool is also a PWA, so you can install it for offline use.
- Which regex flags are supported?
- The tool supports g (global), i (case-insensitive), m (multiline), s (dotAll), and u (unicode) — all standard JavaScript RegExp flags.
- Can I use capture groups in the replacement string?
- Yes. Use $1, $2, … in the replacement field to reference capture groups from your pattern — just like JavaScript's String.replace().