I’ve a really poorly performing piece of regex, currently it makes Firefox, Chrome and

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Editorial Team

Asked: May 14, 20262026-05-14T09:35:30+00:00 2026-05-14T09:35:30+00:00

I’ve a really poorly performing piece of regex, currently it makes Firefox, Chrome and IE hang for a period of time.

Here’s the reg-ex:

 ^([a-zA-Z0-9]+[/]?)+[a-zA-Z0-9]+$

It’s kind of a url matcher, but should only match the requested path (not starting with or ending with a slash).

Valid examples:

Invalid examples:

Using the regex above over all three browsers and using two or more slashes causes the browsers to hang.

It’s obviously a poorly formed reg-ex, but can anyone help build a better one?

Thanks,

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Editorial Team · Answer 1 · 2026-05-14T09:35:31+00:00

Editorial Team

A better one would be more deterministic, and without capturing groups:

^[a-zA-Z0-9]+(?:/[a-zA-Z0-9]+)*$

This way you don’t have overlapping groups, and you’re not capturing things unnecessarily.

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