What is the difference between greedy and lazy regex matching?

Greedy and lazy quantifiers control how much text a regex pattern consumes.

Greedy matching (default):

Quantifiers like *, +, and {n,m} are greedy by default:*

• They match as much text as possible
• <.*> matching <div>text</div> captures the entire string, not individual tags
• The pattern expands as far as it can while still allowing the overall match to succeed*

Lazy (non-greedy) matching:

Add ? after a quantifier to make it lazy:

• *?, +?, {n,m}? match as little as possible
• <.*?> matching <div>text</div> captures <div> first, then </div> separately
• The pattern stops as soon as the condition is satisfied

Practical example:

Extracting text between HTML tags:

• Greedy: <div>(.*)</div> on <div>A</div><div>B</div> matches A</div><div>B
• Lazy: <div>(.*?)</div> correctly matches A first, then B separately

Performance considerations:

• Greedy matching can be faster in some regex engines
• Lazy matching prevents common errors when working with markup
• Choose based on your specific matching needs, not just performance

Common pitfall:

The most common regex mistake is using greedy quantifiers when extracting content between delimiters. Always consider if lazy matching would be more appropriate for your use case.