laravel specified key was too long

use Illuminate\Support\Facades\Schema;
public function boot()
{
    Schema::defaultStringLength(191);
}

use Illuminate\Support\Facades\Schema;

public function boot()
{
    Schema::defaultStringLength(191);
}

'charset' => 'utf8',
'collation' => 'utf8_unicode_ci',

'charset' => 'utf8mb4',
'collation' => 'utf8mb4_unicode_ci',