woocommerce/plugins/woocommerce-admin/client/header/style.scss

.woocommerce-layout__header {
	background: $studio-white;
	box-sizing: border-box;
	padding: 0;
	position: fixed;
	width: calc(100% - 160px);
	top: $adminbar-height;
	z-index: 1001; /* on top of #wp-content-editor-tools */

	&.is-scrolled {
		box-shadow: $header-scroll-shadow;
	}

	.woocommerce-layout__header-wrapper {
		display: flex;
		align-items: center;
		min-height: $header-height;
	}

	@include breakpoint( '<782px' ) {
		flex-flow: row wrap;
		top: $adminbar-height-mobile;
		width: 100%;
	}

	@include breakpoint( '782px-960px' ) {
		width: calc(100% - 36px);
	}

	.woocommerce-layout__header-breadcrumbs-wrapper {
		display: flex;
		justify-content: space-between;
		flex-direction: row;
	}

	.woocommerce-layout__header-heading {
		display: flex;
		align-items: center;
		padding: 0 0 0 $fallback-gutter-large;
		padding: 0 0 0 $gutter-large;
		flex: 1 auto;
		height: $header-height;
		background: $studio-white;
		font-weight: 600;
		font-size: 14px;
		text-transform: capitalize;
	}
}

.is-wp-toolbar-disabled .woocommerce-layout__header {
	top: 0;
}

.has-woocommerce-navigation .woocommerce-layout__header {
	left: 0;
	width: 100%;
}

.woocommerce-page {
	#contextual-help-link-wrap,
	#screen-options-link-wrap {
		margin-top: -1px;
	}
}