What are flags like g, i, m?

g (global) finds all matches, not just the first. i (case-insensitive) ignores case. m (multiline) makes ^ and $ match start/end of each line. Combine them: /pattern/gi.

What is the difference between * and + ?

* matches zero or more occurrences (the preceding item is optional). + matches one or more (at least one required). For example, \d* matches '' and '123', while \d+ requires at least one digit.

How do I match a literal dot or bracket?

Escape special characters with a backslash: \. matches a literal dot, \[ matches a literal bracket. Special characters that need escaping: . * + ? ^ $ { } [ ] ( ) | \

What are capture groups used for?

Parentheses () create capture groups that extract specific parts of a match. For example, (\d{4})-(\d{2})-(\d{2}) captures year, month, and day separately from a date string.

Testador de Expressões Regulares

Teste expressões regulares em texto de exemplo com destaque de correspondências em tempo real.

Padrão

Flags

Texto de teste

What is This Tool?

Regular expressions (regex) are patterns used to match character combinations in strings. They are essential for text searching, validation, and manipulation in programming. This tool lets you test patterns against sample text and see matches highlighted in real-time.

Formula

Common regex syntax:
  .     = any character
  \d    = digit (0-9)
  \w    = word character (a-z, A-Z, 0-9, _)
  \s    = whitespace
  *     = 0 or more
  +     = 1 or more
  ?     = 0 or 1
  [abc] = character class
  ^/$   = start/end of string
  ()    = capture group

Worked Examples

1. Match email addresses

Given: Pattern: [\w.+-]+@[\w-]+\.[\w.-]+

[\w.+-]+ matches the local part (before @)

@ matches the literal @ symbol

[\w-]+\.[\w.-]+ matches the domain

Result: Matches: user@example.com, john.doe+tag@mail.co.uk

2. Extract phone numbers

Given: Pattern: \d{3}[-.]?\d{3}[-.]?\d{4}

\d{3} matches 3 digits

[-.]? optionally matches dash or dot separator

Repeats for all groups

Result: Matches: 555-123-4567, 555.123.4567, 5551234567

3. Validate hex colors

Given: Pattern: ^#?([0-9A-Fa-f]{3}|[0-9A-Fa-f]{6})$

^#? optionally matches leading #

[0-9A-Fa-f]{3} matches 3-digit shorthand

| or [0-9A-Fa-f]{6} matches full 6-digit

Result: Matches: #FFF, #FF5733, aabbcc

Frequently Asked Questions