On a site I am working on I have a requirement that usernames not

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Editorial Team

Asked: May 16, 20262026-05-16T08:46:34+00:00 2026-05-16T08:46:34+00:00

On a site I am working on I have a requirement that usernames not start with <alpha><alpha>_

So these should not be allowed:

But these should be ok:

In the framework I am using, I am only able to validate against matching regular expression, not non-matching. So far I have come up with this:

"/^([^A-Za-z0-9]{2}\_|[A-Za-z0-9]{3,27})/"

This works for most items, but fails on “__SU_Coolguy”.

Any help on this regex would be highly appreciated. 🙂

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Editorial Team · Answer 1 · 2026-05-16T08:46:35+00:00

Editorial Team

Your regex would be /^(?![a-zA-Z0-9]{2}_)/. It means “start with not {two alphanumeric characters and an underscore}”.

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