Regex Tester & Debugger

A regular expression (regex) is a sequence of characters that defines a search pattern. Regex is used for:

Pattern matching: Find text that matches specific patterns (emails, phone numbers, URLs)
Validation: Verify input formats (passwords, credit cards, dates)
Search and replace: Find and modify text in documents or code
Data extraction: Pull specific information from logs, HTML, or datasets
Security: Detect malicious patterns, filter input, prevent injection attacks

Used in programming languages (JavaScript, Python, PHP, Java), text editors, command line tools (grep, sed), and security tools.

Regular Expression Pattern Flags

Common Presets

Test String

.

Any character except newline

\d

Digit (0-9)

\w

Word character (a-z, A-Z, 0-9, _)

\s

Whitespace (space, tab, newline)

^

Start of string/line

$

End of string/line

*

0 or more repetitions

+

1 or more repetitions

?

0 or 1 (optional)

{n,m}

Between n and m repetitions

[abc]

Character class (a, b, or c)

(group)

Capture group

a|b

Alternation (a or b)

\b

Word boundary

(?=...)

Positive lookahead

(?!...)

Negative lookahead