5 Signs Your Regex Is Wrong (and How to Spot Them in Seconds)

We've all been there. You write a regex, it looks correct, you deploy it... and then the bug reports roll in. Regex is deceptively tricky — what looks right often contains subtle flaws that only surface with specific inputs. Here are five telltale signs your pattern needs fixing, and how to catch them before they hit production.

1. It Matches Way More Than You Expected

This is the #1 regex gotcha. You write <.*> to match HTML tags, but it swallows the entire <div>hello</div><span>world</span> in one match. The culprit? Greedy quantifiers. By default, * and + match as much as possible. Add ? after the quantifier to make it lazy: <.*?> matches each tag individually.

Spot it: A visual regex tester with match highlighting makes this instantly obvious — when one match spans three lines of text, you know something's off.

2. It Silently Returns Zero Matches