Using reluctant quantifiers (also known as lazy or non-greedy quantifiers) in patterns can often lead to needless backtracking, making the regex needlessly inefficient and potentially vulnerable to catastrophic backtracking. Particularly when using .*? or .+? to match anything up to some terminating character, it is usually a better idea to instead use a greedily or possessively quantified negated character class containing the terminating character. For example <.+?> should be replaced with <[^>]++>.

Noncompliant Code Example

<.+?>
".*?"

Compliant Solution

<[^>]++>
"[^"]*+"

or

<[^>]+>
"[^"]*"

Exceptions

This rule only applies in cases where the reluctant quantifier can easily be replaced with a negated character class. That means the repetition has to be terminated by a single character or character class. Patterns such as the following, where the alternatives without reluctant quantifiers are more complicated, are therefore not subject to this rule:

<!--.*?-->
/\*.*?\*/