jellyfin-web/dashboard-ui/bower_components/emby-webcomponents/emby-textarea/emby-textarea.css

.emby-textarea {
    display: block;
    margin: 0;
    margin-bottom: 0 !important;
    background: none;
    border: 1px solid #383838;
    border-width: 0 0 1px 0;
    /* Prefixed box-sizing rules necessary for older browsers */
    -webkit-box-sizing: border-box;
    -moz-box-sizing: border-box;
    box-sizing: border-box;
    /* Remove select styling */
    /* Font size must the 16px or larger to prevent iOS page zoom on focus */
    font-size: inherit;
    /* General select styles: change as needed */
    font-family: inherit;
    font-weight: inherit;
    color: inherit;
    padding: .35em 0 .3em 0;
    cursor: pointer;
    outline: none !important;
    width: 100%;
    background-color: transparent;
    border-radius: 0;
}

.inputContainer {
    margin-bottom: 1.8em;
}

.textareaLabel {
    display: inline-block;
    transition: all .2s ease-out;
}

.textareaLabelFocused {
    color: #52B54B;
}

.emby-textarea-selectionbar {
    height: 2px;
    transform: scale(.01, 1);
    transition: transform .25s ease-out;
    position: relative;
    top: -1px;
    margin-bottom: .5em;
    -webkit-transform-origin: center center;
    transform-origin: center center;
}

.emby-textarea:focus + .emby-textarea-selectionbar {
    background-color: #52B54B;
    transform: none;
}