Where is the validation language file under Laravel 10.x?

If you don't have this file yet you can add it in resources/lang/en. Add a new file validation.php with this content and do the same for other desired languages

<?php

return [
    'required' => 'The :attribute field is required.',
    'email' => 'The :attribute field must be a valid email address.',
    // add more validation message keys and strings as needed
];