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Editorial Team
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Asked: 2026-06-12T22:25:36+00:00

I am having a bit of a hard time with a password requirement regular

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I am having a bit of a hard time with a password requirement regular expression for an ASP.NET project

Out requirements are the following

  • Must be at least 8 characters
  • Must have at least 3 of the 4 following:
    • Have at least 1 UPPERCASE letter
    • Have at least 1 lowercase letter
    • Have at least 1 special character
    • Have at least 1 number

The regular expression I am using is as follows (this is escaped and encoded for use in the web.config xml file:

passwordStrengthRegularExpression="^.*(?=.{8,})(?=.*[a-zA-Z])(?=.*\d)(?=.*[!@#$%^&*()\?\+\,\-\.\/\:\:\;\<\=\>\[\]\\_\`\{\|\}\~\"\']).*$"

I cant figure out how to allow for one of the requirements to be optional.

the password Reaction7 should be sufficient, but it is rejected because it doesn’t have a special character.

Anyone know what I can do to evaluate the 3 out of 4 requirements other than length?

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1 Answer

  1. Editorial Team

    Not sure I like this solution, but if you’re limited to using only a single regex (which looks like the case), you could enumerate all possibilities with a pipe-or group:

    passwordStrengthRegularExpression="^.*(?=.{8,})((?=.*[A-Z])(?=.*\d)(?=.*[!@#$%^&*()\?\+\,\-\.\/\:\:\;\<\=\>\[\]\\_\`\{\|\}\~\"\'])|(?=.*[a-z])(?=.*\d)(?=.*[!@#$%^&*()\?\+\,\-\.\/\:\:\;\<\=\>\[\]\\_\`\{\|\}\~\"\'])|(?=.*[a-z])(?=.*[A-Z])(?=.*[!@#$%^&*()\?\+\,\-\.\/\:\:\;\<\=\>\[\]\\_\`\{\|\}\~\"\'])|(?=.*[a-z])(?=.*[A-Z])(?=.*\d)).*$"

    It is rather long but does get the job done. Adding a fifth requirement will make this string explode in size though, so it’s not exactly “extendable”.

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