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I want to create a user account on my multi-site installation of Wordpress with a username less than 4 characters. But since Wordpress has a limit of usernames at least being 4 characters, this error message is shown:

Username must be at least 4 characters.

I found a solution involving a mu-plugins folder in the wp-content folder, but it doesn't work. Is there any possible way that would allow me to create a user account with a username less than 4 characters?

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If there are problems with my answer it would be useful to know what didn’t work. I have tested it as a plugin on a multisite and successfully registered the users a, b and c. –  toscho Jul 27 '12 at 12:49
Actually it's not about your answer being unable to solve my problem. It was just not very useful to me, personally, since I am new to Wordpress. –  Ratul Jul 29 '12 at 19:29
Just save the code as shortnames.php in your plugin directory and activate it. –  toscho Jul 29 '12 at 19:37
Thanks for taking your time to help me. –  Ratul Jul 29 '12 at 19:47

1 Answer 1

up vote 6 down vote accepted

You can filter 'wpmu_validate_user_signup' and check if the error code matches the 4 character warning. Then just unset the error code.

Sample plugin:

<?php # -*- coding: utf-8 -*-
/* Plugin Name: Allow short user names for multi site. */

add_filter( 'wpmu_validate_user_signup', 'wpse_59760_short_user_names' );

 * Allow very short user names.
 * @wp-hook wpmu_validate_user_signup
 * @param   array $result
 * @return  array
function wpse_59760_short_user_names( $result )
    $error_name = $result[ 'errors' ]->get_error_message( 'user_name' );
    if ( empty ( $error_name )
        or $error_name !== __( 'Username must be at least 4 characters.' )
        return $result;

    unset ( $result[ 'errors' ]->errors[ 'user_name' ] );
    return $result;
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