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Regex Tester

Test and debug regular expressions with real-time match highlighting

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Quick Flags

Common Patterns

Quick Reference

Characters

  • . Any character
  • \d Digit (0-9)
  • \w Word char (a-z, 0-9, _)
  • \s Whitespace

Quantifiers

  • * 0 or more
  • + 1 or more
  • ? 0 or 1
  • {n,m} Between n and m

Anchors

  • ^ Start of string
  • $ End of string
  • \b Word boundary

Groups

  • (abc) Capture group
  • (?:abc) Non-capture
  • [abc] Character set
  • [^abc] Not in set

Beginner-Friendly Regex Testing Made Simple

Regular expressions can seem intimidating at first, but they become powerful allies once you understand the basics. Our regex tester provides instant visual feedback, showing exactly what your pattern matches in real-time. Whether you are validating user input, searching through logs, or extracting data from text, this tool helps you build and debug patterns with confidence.

Understanding the Basics

At its core, regex is about pattern matching. Simple patterns match literal text: typing"cat" matches the word"cat" in your text. Special characters add flexibility: \d matches any digit, \w matches any letter or number, and . matches any character. Combine these with quantifiers like + (one or more) or * (zero or more) to match variable-length content like phone numbers or email addresses.

Working with Flags

Flags change how your pattern behaves. The global flag (g) finds every match instead of stopping at the first one. Case-insensitive (i) treats uppercase and lowercase letters the same, so"ABC" matches"abc". Multiline (m) is useful when working with text that has multiple lines, allowing ^ and $ to match line beginnings and endings, not just the string boundaries.

Capture Groups Explained

Parentheses create capture groups that extract specific parts of a match. If you match a date with (\d{4})-(\d{2})-(\d{2}), you get three groups: year, month, and day. This is incredibly useful for data extraction, reformatting, and search-and-replace operations. Our tool displays each group separately so you can verify your pattern captures exactly what you need.

Common Pitfalls and Solutions

The most common mistake is forgetting to escape special characters. A period (.) matches any character, so to match an actual period you need \. instead. Similarly, use \$ for dollar signs and \( for parentheses. If your pattern unexpectedly matches nothing, check for typos, missing escapes, or try simplifying to isolate the problem. Start with a basic pattern and add complexity gradually.

Privacy and Security

All regex testing occurs entirely within your browser. Your patterns and test strings never leave your device or get sent to any server. This makes our tool safe for testing patterns against sensitive data like customer information, API keys, or proprietary content. Simply close the browser tab when finished and all data disappears.

$ faq

What is a regular expression (regex)? ▸
A regular expression is a sequence of characters that defines a search pattern. It is used to find, match, or replace text in strings. For example, the pattern"[0-9]+" matches one or more digits. Regex is widely used in programming, text editors, and data validation.
What do the regex flags mean? ▸
Flags modify how the regex pattern works:"g" (global) finds all matches instead of stopping at the first one."i" (case-insensitive) ignores uppercase/lowercase differences."m" (multiline) makes ^ and $ match the start/end of each line, not just the whole string.
What are capture groups? ▸
Capture groups are parts of your pattern enclosed in parentheses (). They let you extract specific portions of a match. For example, in the pattern"(\d{3})-(\d{4})", matching"555-1234" gives you two groups:"555" and"1234". Groups are numbered starting from 1.
Why is my regex not matching anything? ▸
Common reasons include: forgetting to escape special characters like dots (use \. instead of .), missing the global flag to find all matches, case sensitivity issues (try the"i" flag), or the pattern syntax being incorrect. Use our preset examples as a starting point.
What special characters need escaping? ▸
These characters have special meaning in regex and need a backslash to match literally: . * + ? ^ $ { } [ ] ( ) | \ /. For example, to match a period, use \. instead of just a dot. To match a dollar sign, use \$.
How do I match an email address? ▸
A simple email pattern is [a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}. This matches most common email formats. However, email validation with regex can be complex—for production use, consider additional validation methods.
Is my data private when using this tool? ▸
Yes, all regex testing happens entirely in your browser using JavaScript. Your patterns and test strings are never sent to any server. When you close or refresh the page, all data is cleared from memory. Your sensitive test data remains completely private.