Regex Quantifiers — Greedy vs Lazy Matching Explained

Regex Quantifiers: Greedy vs Lazy

Quantifiers control how many times a preceding element is matched. Understanding the difference between greedy and lazy modes is crucial for writing correct patterns.

Standard Quantifiers

Quantifier	Meaning
*	Zero or more
+	One or more
?	Zero or one (optional)
{n}	Exactly n times
{n,}	n or more times
{n,m}	Between n and m times

Greedy Mode (Default)

By default, quantifiers are greedy: they match as many characters as possible while still allowing the overall pattern to succeed. For example, given the string <b>bold</b>, the pattern <.+> matches the entire string <b>bold</b> because .+ consumes everything it can.

Lazy Mode (Non-Greedy)

Adding ? after a quantifier makes it lazy: it matches as few characters as possible. The pattern <.+?> applied to <b>bold</b> matches <b> first, then </b> separately.

Greedy	Lazy	Behavior
*	*?	Zero or more, prefer fewer
+	+?	One or more, prefer fewer
?	??	Zero or one, prefer zero

When to Use Each

• Greedy is usually fine for simple patterns where there is no ambiguity
• Lazy is essential when matching paired delimiters (HTML tags, quotes, brackets)
• Consider using negated character classes as an alternative: <[^>]+> is often clearer and faster than <.+?>

Performance Consideration

Lazy quantifiers can cause excessive backtracking on long strings. When possible, prefer negated character classes or atomic grouping for better performance.