← All Tools
Regex Tester Online — Test Regular Expressions
Test regular expressions online with real-time matching. Free regex tester supports flags, groups, and common patterns. No signup.
//
Common patterns:
Test regular expressions against sample text in real time. See matches highlighted as you type, with capture groups and match indices displayed for debugging.
How to use Regex Tester Online — Test Regular Expressions
- Enter your regex pattern in the pattern field and choose flags (g, i, m, s) as needed.
- Paste or type your test string in the input area.
- Review highlighted matches and capture group details in the output panel.
Features
- Live match highlighting as you edit the pattern or test string.
- Supports global, case-insensitive, multiline, and dotall flags.
- Displays capture groups and their match positions for debugging.
- Common regex reference cheat sheet included.
FAQ
Which regex flavor does this tester use?
It uses JavaScript's built-in RegExp engine, which covers most common patterns. Some advanced features like lookbehind vary by browser version.
Can I test regex with capture groups?
Yes. Capture groups are displayed with their matched values and positions so you can verify your pattern extracts the right data.
How do I match a literal backslash in regex?
Use \\ in the pattern. Backslash is an escape character in regex, so you need two backslashes to match one literal backslash.
Related Articles
Developer
Regex Cheat Sheet: Common Patterns for Everyday Use
Regex keeps slipping your mind? This guide breaks down the patterns you'll actually use — email, phone, URLs — with a free tester.
Developer
The Regex That Passed in the Tester and Broke in Production
Five real reasons a regular expression behaves differently in your app than in an online tester: the global-flag statefulness bug, the trailing-newline dollar, greedy quantifiers, the ASCII-only \d, and catastrophic backtracking.
Related Tools
JSON Formatter Online — Format & Validate JSON Free
Format and validate JSON online for free. Paste messy JSON and get clean, indented output instantly. No signup, runs in your browser.
Base64 Encoder & Decoder Online — Free Tool
Encode text to Base64 or decode Base64 back to text. Free online tool runs entirely in your browser. No upload, no signup. Instant results.
URL Encoder & Decoder Online — Free Percent Encoding
Encode or decode URLs with percent-encoding. Free online tool handles query strings, special characters, and Unicode instantly. No signup required.
HTML Entities Encoder & Decoder Online — Free
Encode special characters to HTML entities or decode them back. Free online tool for web developers. No signup, instant results, runs in browser.