Question 1

What does \d mean in regex?

Accepted Answer

\d matches any single digit character from 0 to 9. It is equivalent to the character class [0-9].

Question 2

What does \w mean in regex?

Accepted Answer

\w matches any word character: letters (a-z and A-Z), digits (0-9), and the underscore character (_). It is equivalent to [a-zA-Z0-9_].

Question 3

What does the + quantifier mean in regex?

Accepted Answer

The + quantifier means 'one or more times'. The preceding element must appear at least once. For example, \d+ matches one or more digits.

Question 4

What is the difference between .* and .+?

Accepted Answer

Both match any character, but .* matches zero or more characters (can match an empty string), while .+ requires at least one character.

Question 5

What does ^ mean in regex?

Accepted Answer

The ^ anchor asserts that the match must start at the beginning of the string. In multiline mode it matches the start of each line. Inside a character class like [^abc] it means 'anything except'.

^	start of string
$	end of string
\b	word boundary
\B	non-word boundary

\d	any digit (0–9)
\D	any non-digit
\w	letter, digit, or _
\W	non-word character
\s	whitespace
\S	non-whitespace
\n	newline
\t	tab

*	0 or more times
+	1 or more times
?	0 or 1 time
{n}	exactly n times
{n,m}	n to m times
{n,}	n or more times
*?	lazy (as few as possible)

Regex Explainer

Quick Reference

Anchors

Common escapes

Quantifiers

Regex Explainer

Quick Reference

Anchors

Common escapes

Quantifiers

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