More Information
It can be used to customize the built-in WordPress login form. Use in conjunction with ‘login_head’
(for validation).

Basic Examples
This example demonstrates how to add a new field to the login form. Keep in mind that this won’t be saved
automatically. You will still need to set up validation rules and manually handle saving of the additional
form fields.

add_action( 'login_form', 'wpdocs_myplugin_add_login_fields' );

function wpdocs_myplugin_add_login_fields() {

    // Get and set any values already sent
    $user_extra = ( isset( $_POST['user_extra'] ) ) ? $_POST['user_extra'] : '';
    
    <p>
        <label for="user_extra"><?php
_e('Extra Field', 'mydomain') ?><br />
            <input type="text" name="user_extra" id="user_extra" class="input" value="<?php
echo esc_attr( stripslashes( $user_extra ) );
?>" size="25" /></label>
    </p>

}

The following example demonstrates how to translate the login form, page, fields or labels. Choose the
codes/blocks for translation accurately, otherwise the above function may change other parts
of the login page.

function wpdocs_my_translatorr2() {

  $your_content = ob_get_contents();
  $your_content = preg_replace( '/\<label for="user_login"\>(.*?)\<br/', 'Usernumia: ', $your_content );
  $your_content = preg_replace( '/\<label for="user_pass"\>(.*?)\<br/', 'Passwiert:', $your_content );

  ob_get_clean();

  echo $your_content;

}

add_action( 'login_form', 'wpdocs_my_translatorr2' );

Simple example to add a note or bit of text below the password field:

add_action( 'login_form', 'wpdocs_login_extra_note' );

function wpdocs_login_extra_note() {

    //Adding the text
    <p>You can type a little note to those logging in here.</p>
    
}

For form validation, use ‘login_head‘.