nextcloud/core/css/fonts.scss

@font-face {
	font-family: 'Open Sans';
	font-style: normal;
	font-weight: normal;
	src: local('Open Sans'), local('OpenSans'),
		url('../fonts/OpenSans.woff') format('woff'),
		url('../fonts/OpenSans.ttf') format('ttf');
}

@font-face {
	font-family: 'Open Sans';
	font-style: normal;
	font-weight: bold;
	src: local('Open Sans Bold'), local('OpenSans-Bold'),
		url('../fonts/OpenSans-Bold.woff') format('woff'),
		url('../fonts/OpenSans-Bold.ttf') format('ttf');
}