diff --git a/lib/dev-build.js b/lib/dev-build.js
index 71ef7e7..bf1dc61 100644
--- a/lib/dev-build.js
+++ b/lib/dev-build.js
@@ -1,11 +1,14 @@
 const webpack = require('webpack');
 const webpackDevMiddleware = require('webpack-dev-middleware');
+const {getFilenameFromUrl} = require('webpack-dev-middleware/lib/util');
 const webpackHotMiddleware = require('webpack-hot-middleware');
 const {reactive, computed} = require('@vue/reactivity');
 const {createBundleRenderer} = require('vue-server-renderer');
 const {createFsFromVolume, Volume} = require('memfs');
 const path = require('path');
 const consola = require('consola');
+const getETag = require('etag');
+const hasOwnProp = require('has-own-prop');
 
 function Deferred() {
 	this.isResolved = false;
@@ -77,12 +80,56 @@ function createClientBuild(state, clientConfig) {
 		stats: 'none',
 	});
 
+	const etagRegistry = new Map();
+
+	function computeEtags(assets) {
+		for (const assetId in assets) {
+			if (!hasOwnProp(assets, assetId)) {
+				continue;
+			}
+
+			const fsPath = assets[assetId].existsAt;
+			const etag = getETag(assets[assetId].source());
+			etagRegistry.set(fsPath, etag);
+		}
+	}
+
 	const middlewares = {
-		devMiddleware,
+		devMiddleware({url, headers}, response) {
+			const filename = getFilenameFromUrl(
+				devMiddleware.context.options.publicPath,
+				devMiddleware.context.compiler,
+				url,
+			);
+
+			const ifNoneMatch = headers['if-none-match'];
+			if (ifNoneMatch) {
+				const assetEtag = etagRegistry.get(filename);
+				if (assetEtag && assetEtag === ifNoneMatch) {
+					response.statusCode = 304;
+					response.end();
+					return;
+				}
+			}
+
+			response.send = result => {
+				const etag = etagRegistry.get(filename);
+				if (etag) {
+					response.setHeader('ETag', etag);
+				}
+
+				response.setHeader('Cache-Control', 'nocache');
+				response.end(result);
+			};
+
+			Reflect.apply(devMiddleware, this, arguments);
+		},
 		hotMiddleware: webpackHotMiddleware(clientCompiler),
 	};
 
 	const onDone = stats => {
+		computeEtags(stats.compilation.assets);
+
 		stats = stats.toJson();
 
 		if (stats.errors.length > 0) {
diff --git a/lib/init-server.js b/lib/init-server.js
index cde9f07..d86365b 100644
--- a/lib/init-server.js
+++ b/lib/init-server.js
@@ -24,11 +24,16 @@ function initServer({
 
 			try {
 				const html = await renderer.value.renderToString(context);
+				response.setHeader('Content-Type', 'text/html');
 				response.end(html);
 			} catch (error) {
 				const {code = 500, message = 'Internal Server Error'} = error;
 				response.statusCode = code;
-				response.end(`Error: ${message}`);
+				response.setHeader('Content-Type', 'application/json');
+				response.end(JSON.stringify({
+					code,
+					message,
+				}));
 
 				if (!error.code) {
 					console.error(error);
diff --git a/package-lock.json b/package-lock.json
index 251e686..6c24974 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -2486,6 +2486,11 @@
       "integrity": "sha512-kVscqXk4OCp68SZ0dkgEKVi6/8ij300KBWTJq32P/dYeWTSwK41WyTxalN1eRmA5Z9UU/LX9D7FWSmV9SAYx6g==",
       "dev": true
     },
+    "etag": {
+      "version": "1.8.1",
+      "resolved": "https://registry.npmjs.org/etag/-/etag-1.8.1.tgz",
+      "integrity": "sha1-Qa4u62XvpiJorr/qg6x9eSmbCIc="
+    },
     "events": {
       "version": "3.2.0",
       "resolved": "https://registry.npmjs.org/events/-/events-3.2.0.tgz",
@@ -3126,6 +3131,11 @@
       "resolved": "https://registry.npmjs.org/has-flag/-/has-flag-3.0.0.tgz",
       "integrity": "sha1-tdRU3CGZriJWmfNGfloH87lVuv0="
     },
+    "has-own-prop": {
+      "version": "2.0.0",
+      "resolved": "https://registry.npmjs.org/has-own-prop/-/has-own-prop-2.0.0.tgz",
+      "integrity": "sha512-Pq0h+hvsVm6dDEa8x82GnLSYHOzNDt7f0ddFa3FqcQlgzEiptPqL+XrOJNavjOzSYiYWIrgeVYYgGlLmnxwilQ=="
+    },
     "has-symbols": {
       "version": "1.0.1",
       "resolved": "https://registry.npmjs.org/has-symbols/-/has-symbols-1.0.1.tgz",
diff --git a/package.json b/package.json
index cfafe8c..09c9394 100644
--- a/package.json
+++ b/package.json
@@ -37,7 +37,9 @@
     "compression": "^1.7.4",
     "connect": "^3.7.0",
     "consola": "^2.15.0",
+    "etag": "^1.8.1",
     "get-port": "^5.1.1",
+    "has-own-prop": "^2.0.0",
     "lodash": "^4.17.20",
     "memfs": "^3.2.0",
     "minimist": "^1.2.5",