webpack · OskarEichler · Aug 28, 2026 · Aug 29, 2026 · Aug 29, 2026
diff --git a/.changeset/server-reporting-overhead.md b/.changeset/server-reporting-overhead.md
@@ -0,0 +1,5 @@
+---
+"webpack-dev-server": patch
+---
+
+Collect only the statistics needed by the asset report, reuse directory-listing middleware, and serialize each WebSocket broadcast only once.
diff --git a/lib/Server.js b/lib/Server.js
@@ -2171,14 +2171,22 @@ class Server {
             '<!DOCTYPE html><html><head><meta charset="utf-8"/></head><body>',
           );
 
+          const isMultiStats =
+            typeof (/** @type {MultiStats} */ (stats).stats) !== "undefined";
+          const jsonStats = /** @type {Stats | MultiStats} */ (stats).toJson({
+            all: false,
+            children: isMultiStats,
+            assets: true,
+            publicPath: true,
+          });
+
           /**
            * @type {StatsCompilation[]}
            */
-          const statsForPrint =
-            typeof (/** @type {MultiStats} */ (stats).stats) !== "undefined"
-              ? /** @type {NonNullable<StatsCompilation["children"]>} */
-                (/** @type {MultiStats} */ (stats).toJson().children)
-              : [/** @type {Stats} */ (stats).toJson()];
+          const statsForPrint = isMultiStats
+            ? /** @type {NonNullable<StatsCompilation["children"]>} */
+              (jsonStats.children)
+            : [jsonStats];
 
           res.write("<h1>Assets Report:</h1>");
 
@@ -2411,6 +2419,11 @@ class Server {
       for (const staticOption of staticOptions) {
         for (const publicPath of staticOption.publicPath) {
           if (staticOption.serveIndex) {
+            const serveIndexMiddleware = serveIndex(
+              staticOption.directory,
+              staticOption.serveIndex,
+            );
+
             middlewares.push({
               name: "serve-index",
               path: publicPath,
@@ -2426,11 +2439,7 @@ class Server {
                   return next();
                 }
 
-                serveIndex(
-                  staticOption.directory,
-                  /** @type {ServeIndexOptions} */
-                  (staticOption.serveIndex),
-                )(req, res, next);
+                serveIndexMiddleware(req, res, next);
               },
             });
           }
@@ -3339,10 +3348,14 @@ class Server {
    * @param {EXPECTED_ANY=} params params
    */
   sendMessage(clients, type, data, params) {
+    /** @type {string | undefined} */
+    let message;
+
     for (const client of clients) {
       // `ws` uses `WebSocket.OPEN`, which is `1`
       if (client.readyState === 1) {
-        client.send(JSON.stringify({ type, data, params }));
+        message ??= JSON.stringify({ type, data, params });
+        client.send(message);
       }
     }
   }

diff --git a/test/e2e/built-in-routes.test.js b/test/e2e/built-in-routes.test.js
@@ -1,5 +1,6 @@
 import { afterEach, beforeEach, describe, it } from "node:test";
 import { expect } from "expect";
+import { spyOn } from "jest-mock";
 import webpack from "webpack";
 import Server from "../../lib/Server.js";
 import config from "../fixtures/client-config/webpack.config.js";
@@ -61,6 +62,11 @@ describe("Built in routes", () => {
     });
 
     it("should handle GET request to directory index and list all middleware directories", async (t) => {
+      const stats = await new Promise((resolve) => {
+        server.middleware.waitUntilValid(resolve);
+      });
+      const toJsonSpy = spyOn(stats, "toJson");
+
       page
         .on("console", (message) => {
           consoleMessages.push(message);
@@ -85,6 +91,14 @@ describe("Built in routes", () => {
       t.assert.snapshot(consoleMessages.map((message) => message.text()));
 
       t.assert.snapshot(pageErrors);
+
+      expect(toJsonSpy).toHaveBeenCalledWith({
+        all: false,
+        children: false,
+        assets: true,
+        publicPath: true,
+      });
+      toJsonSpy.mockRestore();
     });
 
     it("should handle HEAD request to directory index", async (t) => {
@@ -191,6 +205,11 @@ describe("Built in routes", () => {
     });
 
     it("should handle GET request to directory index and list all middleware directories", async (t) => {
+      const stats = await new Promise((resolve) => {
+        server.middleware.waitUntilValid(resolve);
+      });
+      const toJsonSpy = spyOn(stats, "toJson");
+
       page
         .on("console", (message) => {
           consoleMessages.push(message);
@@ -215,6 +234,14 @@ describe("Built in routes", () => {
       t.assert.snapshot(consoleMessages.map((message) => message.text()));
 
       t.assert.snapshot(pageErrors);
+
+      expect(toJsonSpy).toHaveBeenCalledWith({
+        all: false,
+        children: true,
+        assets: true,
+        publicPath: true,
+      });
+      toJsonSpy.mockRestore();
     });
   });
 });