How can I validate fields in registration form ?

Question

The registration is important part for an admin . Admin wants the data should be in correct form and all fields .

How can I apply validations ?

1. User fill fields atleast 3 length.

Comments

To validate default registration fields like username, email is easy. https://github.com/q2a/question2answer/blob/dev/qa-include/plugins/qa-filter-basic.php          is the in-built plugin that governs validation jobs. You will create a new FILTER plugin and replicate the needed functions in that qa-filter-basic.php file.

Something like  if (strlen($handle) < 4) return "Usernames must contain more than 3 characters.";

I haven't tried with custom reg fields like Fullname, Location... In theory, it should work if you know the variable names.

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This should probably be an answer.