diff --git a/cmake/script/EmbedResources.cmake b/cmake/script/EmbedResources.cmake
index 4dba50a..54870b5 100644
--- a/cmake/script/EmbedResources.cmake
+++ b/cmake/script/EmbedResources.cmake
@@ -1,6 +1,8 @@
 set(OUTPUT_CONTENT "#include <stddef.h>\n")
 foreach(INPUT_FILE ${INPUT_FILES})
 	file(READ ${SOURCE_DIR}/${INPUT_FILE} INPUT_DATA_HEX HEX)
+	string(SHA256 INPUT_HASH "${INPUT_DATA_HEX}")
+	string(SUBSTRING "${INPUT_HASH}" 0 12 INPUT_HASH)
 	
 	string(REGEX REPLACE "[^a-zA-Z0-9_]" "_" OUTPUT_VAR ${INPUT_FILE})
 	
@@ -11,7 +13,8 @@ foreach(INPUT_FILE ${INPUT_FILES})
 	string(REGEX REPLACE "[^\n][^\n]" "\\\\x\\0" INPUT_DATA_C_ARRAY "${INPUT_DATA_C_ARRAY}")
 	string(REGEX REPLACE "\n" "\"\n\"" INPUT_DATA_C_ARRAY "${INPUT_DATA_C_ARRAY}")
 	
-	string(APPEND OUTPUT_CONTENT "\nstatic const char ${OUTPUT_VAR}[]=\n\"${INPUT_DATA_C_ARRAY}\\0\";\nstatic const size_t ${OUTPUT_VAR}_sz=${INPUT_DATA_LEN};\n")
+	string(APPEND OUTPUT_CONTENT "\nstatic const char ${OUTPUT_VAR}[]=\n\"${INPUT_DATA_C_ARRAY}\\0\";\nstatic const size_t ${OUTPUT_VAR}_sz=${INPUT_DATA_LEN};\nstatic const char ${OUTPUT_VAR}_etag[] = \"\\\"${INPUT_HASH}\\\"\";\n")
+	
 endforeach()
 
 file(WRITE ${OUTPUT_FILE} "${OUTPUT_CONTENT}")
diff --git a/src/datum_api.c b/src/datum_api.c
index 7821a55..d56933a 100644
--- a/src/datum_api.c
+++ b/src/datum_api.c
@@ -486,9 +486,18 @@ bool datum_api_check_admin_password(struct MHD_Connection * const connection, co
 	return datum_api_check_admin_password_httponly(connection);
 }
 
-static int datum_api_asset(struct MHD_Connection * const connection, const char * const mimetype, const char * const data, const size_t datasz) {
+static int datum_api_asset(struct MHD_Connection * const connection, const char * const mimetype, const char * const data, const size_t datasz, const char * const etag) {
+	const char * const if_none_match_header = MHD_lookup_connection_value(connection, MHD_HEADER_KIND, "If-None-Match");
+	if (if_none_match_header && 0 == strcmp(if_none_match_header, etag)) {
+		struct MHD_Response *response = MHD_create_response_from_buffer(0, "", MHD_RESPMEM_PERSISTENT);
+		MHD_add_response_header(response, "Etag", etag);
+		int ret = MHD_queue_response(connection, MHD_HTTP_NOT_MODIFIED, response);
+		MHD_destroy_response(response);
+		return ret;
+	}
 	struct MHD_Response * const response = MHD_create_response_from_buffer(datasz, (void*)data, MHD_RESPMEM_PERSISTENT);
 	MHD_add_response_header(response, "Content-Type", mimetype);
+	MHD_add_response_header(response, "Etag", etag);
 	const int ret = MHD_queue_response (connection, MHD_HTTP_OK, response);
 	MHD_destroy_response (response);
 	return ret;
@@ -1109,11 +1118,11 @@ enum MHD_Result datum_api_answer(void *cls, struct MHD_Connection *connection, c
 		
 		case 'a': {
 			if (!strcmp(url, "/assets/icons/datum_logo.svg")) {
-				return datum_api_asset(connection, "image/svg+xml", www_assets_icons_datum_logo_svg, www_assets_icons_datum_logo_svg_sz);
+				return datum_api_asset(connection, "image/svg+xml", www_assets_icons_datum_logo_svg, www_assets_icons_datum_logo_svg_sz, www_assets_icons_datum_logo_svg_etag);
 			} else if (!strcmp(url, "/assets/icons/favicon.ico")) {
-				return datum_api_asset(connection, "image/x-icon", www_assets_icons_favicon_ico, www_assets_icons_favicon_ico_sz);
+				return datum_api_asset(connection, "image/x-icon", www_assets_icons_favicon_ico, www_assets_icons_favicon_ico_sz, www_assets_icons_favicon_ico_etag);
 			} else if (!strcmp(url, "/assets/style.css")) {
-				return datum_api_asset(connection, "text/css", www_assets_style_css, www_assets_style_css_sz);
+				return datum_api_asset(connection, "text/css", www_assets_style_css, www_assets_style_css_sz, www_assets_style_css_etag);
 			}
 			break;
 		}
@@ -1137,7 +1146,7 @@ enum MHD_Result datum_api_answer(void *cls, struct MHD_Connection *connection, c
 		
 		case 'f': {
 			if (!strcmp(url, "/favicon.ico")) {
-				return datum_api_asset(connection, "image/x-icon", www_assets_icons_favicon_ico, www_assets_icons_favicon_ico_sz);
+				return datum_api_asset(connection, "image/x-icon", www_assets_icons_favicon_ico, www_assets_icons_favicon_ico_sz, www_assets_icons_favicon_ico_etag);
 			}
 			break;
 		}