Cdigo CSS para por plano de fundo no aplicativo

<div class="background"></div> <pre><span><style> .background { position: fixed; margin-top:0; width: 100%; height:100%; top:0; right:0; left: 0%; z-index:-100; filter: brightness(50%); background-image: url("https://images.unsplash.com/photo-1575525351624-d5cbc45a82a1?ixid=MnwxMjA3fDB8MHxwaG90by1wYWdlfHx8fGVufDB8fHx8&ixlib=rb-1.2.1&auto=format&fit=crop&w=710&q=80"); background-size: cover; background-position: center center; }