Test and debug regular expressions in real time with this free online regex tester. See matches highlighted instantly as you type — no signup, no tracking. Runs 100% in your browser.
How to Use This Regex Tester
- Enter your regex pattern in the pattern field
- Set flags (g = global, i = case-insensitive, m = multiline)
- Paste your test string below
- Matches appear instantly as you type
- Use common patterns buttons for quick starts
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Regex Quick Reference
.— any character except newline\d— digit (0-9),\w— word char,\s— whitespace*— 0 or more,+— 1 or more,?— 0 or 1{n,m}— between n and m occurrences[abc]— character class,[^abc]— negated class^— start of string,$— end of string(group)— capture group,(?:group)— non-capturinga|b— alternation (a or b)
Common Regex Flags
g— Global: find all matches, not just the firsti— Case-insensitive matchingm— Multiline:^and$match line boundariess— Dotall:.matches newlines too
Privacy
This regex tester runs entirely in your browser. No data is sent to any server. Safe for testing patterns against sensitive text.
Recommended Reading
Master regular expressions with these essential resources:
- Mastering Regular Expressions — essential reading for learning regex
- Regular Expressions Cookbook — essential reading for regex patterns
- Introducing Regular Expressions — essential reading for getting started with regex
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Frequently Asked Questions
What is a regular expression and when should I use one?
A regular expression (regex) is a pattern-matching syntax used to search, validate, or transform text. Use regex when you need to find complex patterns like email addresses, phone numbers, or specific string formats in your data.
How do I test a regex pattern before using it in production code?
Use an online regex tester to paste your pattern and sample text, then see matches highlighted in real time. This lets you iterate quickly, catch edge cases, and verify capture groups before embedding the regex in your application.
What do common regex symbols like \d, \w, and .* mean?
\d matches any digit (0–9), \w matches any word character (letters, digits, underscore), and .* matches zero or more of any character. These are the building blocks — combine them with quantifiers and anchors to match complex patterns.
Why does my regex match too much or too little text?
Greedy quantifiers like .* match as much text as possible, which often captures more than intended. Switch to lazy quantifiers (.*?) to match the minimum. Also check that you are anchoring with ^ and $ if you want to match the full string.
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