A free online regex tester and debugger that lets you write, test, and visualize regular expressions in real time. See match highlights, capture groups, and pattern explanations — all running in your browser with instant feedback.
Key Features
Real-Time Matching — See matches highlighted instantly as you type
Capture Groups — Color-coded group highlighting with numbered references
Match Details — View match index, length, and captured groups
Error Detection — Immediate feedback on invalid regex patterns
100% Client-Side — All matching runs in your browser via JavaScript RegExp
How to Use
Enter your regular expression pattern in the regex input field.
Type your test string in the text area below.
Matches are highlighted instantly with color-coded capture groups.
View match details including group indices and captured text.
Use Cases
Data Validation:Test patterns for validating emails, phone numbers, URLs, and other input formats.
Search & Replace:Build complex find-and-replace patterns for text editors and code refactoring.
Log Analysis:Write patterns to extract specific data from server logs and error messages.
Web Scraping:Create patterns to extract structured data from HTML and text content.
Tips
Tip: Start with simple patterns and gradually add complexity. Use non-capturing groups (?:...) when you need grouping without capturing.
Tip: Use the test string area with real data from your use case — not just simple examples — to catch edge cases early.
Alternatives
Regex101 — Popular online regex debugger with detailed explanations
VS Code — Built-in regex search in Find & Replace (Ctrl+F)
grep — Command-line regex matching on Linux/Mac
FAQ
A regular expression (regex) is a pattern used to match character combinations in strings. Regex uses special syntax like * (zero or more), + (one or more), ? (optional), and [] (character sets) to define flexible search patterns.
Common issues include: missing escape characters for special characters (like . or *), incorrect use of anchors (^ and $), or forgetting to enable the right flags (like the global flag g for multiple matches). The tester will highlight where matches occur to help debug.
Capture groups are portions of a regex pattern enclosed in parentheses (). They "capture" the matched text so you can extract specific parts of a match. For example, in the pattern (\d+)-(\d+), the first group captures the first number and the second captures the second number.
The core syntax is very similar across languages, but there are differences. JavaScript uses /pattern/flags syntax, Python uses the re module, and some languages support features like named groups or lookaheads differently. This tester uses JavaScript regex syntax.
While technically possible for simple cases, regex is not recommended for parsing HTML. HTML is not a regular language, and regex can fail with nested tags, attributes, and edge cases. Use an HTML parser like DOMParser or cheerio instead.
Related Searches
regex testerregular expression testerregex onlineregex debuggerregex matchregex patternjavascript regexregex test onlineregex validatorregex find and replaceregexp tool