diff --git a/core/core.js b/core/core.js
index 3dde2085..00facd83 100644
--- a/core/core.js
+++ b/core/core.js
@@ -374,27 +374,27 @@ async function wellKnownHandler(request, response, path) {
 	}
 }
 
-function sendData(response, data, type) {
+function sendData(response, data, type, headers) {
 	if (data) {
 		if (startsWithBytes(data, [0xff, 0xd8, 0xff, 0xdb]) ||
 			startsWithBytes(data, [0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10, 0x4a, 0x46, 0x49, 0x46, 0x00, 0x01]) ||
 			startsWithBytes(data, [0xff, 0xd8, 0xff, 0xee]) ||
 			startsWithBytes(data, [0xff, 0xd8, 0xff, 0xe1, null, null, 0x45, 0x78, 0x69, 0x66, 0x00, 0x00])) {
-			response.writeHead(200, {"Content-Type": "image/jpeg", "Content-Length": data.byteLength});
+			response.writeHead(200, Object.assign({"Content-Type": "image/jpeg", "Content-Length": data.byteLength}, headers || {}));
 			response.end(data);
 		} else if (startsWithBytes(data, [0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a])) {
-			response.writeHead(200, {"Content-Type": "image/png", "Content-Length": data.byteLength});
+			response.writeHead(200, Object.assign({"Content-Type": "image/png", "Content-Length": data.byteLength}, headers || {}));
 			response.end(data);
 		} else if (startsWithBytes(data, [0x47, 0x49, 0x46, 0x38, 0x37, 0x61]) ||
 			startsWithBytes(data, [0x47, 0x49, 0x46, 0x38, 0x39, 0x61])) {
-			response.writeHead(200, {"Content-Type": "image/gif", "Content-Length": data.byteLength});
+			response.writeHead(200, Object.assign({"Content-Type": "image/gif", "Content-Length": data.byteLength}, headers || {}));
 			response.end(data);
 		} else {
-			response.writeHead(200, {"Content-Type": type || "text/javascript; charset=utf-8", "Content-Length": data.byteLength});
+			response.writeHead(200, Object.assign({"Content-Type": type || "text/javascript; charset=utf-8", "Content-Length": data.byteLength}, headers || {}));
 			response.end(data);
 		}
 	} else {
-		response.writeHead(404, {"Content-Type": "text/plain; charset=utf-8", "Content-Length": "File not found".length});
+		response.writeHead(404, Object.assign({"Content-Type": "text/plain; charset=utf-8", "Content-Length": "File not found".length}, headers || {}));
 		response.end("File not found");
 	}
 }
@@ -446,16 +446,24 @@ async function blobHandler(request, response, blobId, uri) {
 			if (match = /^\/\~(\w+)\/(\w+)$/.exec(blobId)) {
 				var id = await new Database(match[1]).get('path:' + match[2]);
 				if (id) {
-					data = await getBlobOrContent(id);
-					if (match[3]) {
-						var app = JSON.parse(data);
-						data = app.files[match[3]];
+					if (request.headers['if-none-match'] && request.headers['if-none-match'] == '"' + id + '"') {
+						response.writeHead(304, {});
+						response.end();
+					} else {
+						data = await getBlobOrContent(id);
+						if (match[3]) {
+							var app = JSON.parse(data);
+							data = app.files[match[3]];
+						}
+						sendData(response, data, undefined, {etag: '"' + id + '"'});
 					}
+				} else {
+					sendData(response, data);
 				}
 			} else {
 				data = await getBlobOrContent(blobId);
+				sendData(response, data);
 			}
-			sendData(response, data);
 		} else if (uri == "/save") {
 			let newBlobId = await ssb.blobStore(request.body);
 
@@ -478,23 +486,33 @@ async function blobHandler(request, response, blobId, uri) {
 		} else {
 			var data;
 			var type;
+			var headers;
 			if (match = /^\/\~(\w+)\/(\w+)$/.exec(blobId)) {
 				var db = new Database(match[1]);
 				var id = await db.get('path:' + match[2]);
 				if (id) {
-					data = utf8Decode(await getBlobOrContent(id));
-					var app = JSON.parse(data);
-					data = app.files[uri.substring(1)];
-					data = await getBlobOrContent(data);
-					type = guessType(uri);
+					if (request.headers['if-none-match'] && request.headers['if-none-match'] == '"' + id + '"') {
+						response.writeHead(304, {});
+						response.end();
+					} else {
+						data = utf8Decode(await getBlobOrContent(id));
+						var app = JSON.parse(data);
+						data = app.files[uri.substring(1)];
+						data = await getBlobOrContent(data);
+						type = guessType(uri);
+						headers = {'ETag': '"' + id + '"'};
+						sendData(response, data, type, headers);
+					}
+				} else {
+					sendData(response, data, type, headers);
 				}
 			} else {
 				data = utf8Decode(await getBlobOrContent(blobId));
 				var app = JSON.parse(data);
 				data = app.files[uri.substring(1)];
 				data = await getBlobOrContent(data);
+				sendData(response, data, type, headers);
 			}
-			sendData(response, data, type);
 		}
 	}
 }