diff --git a/default/public/error/url-not-found.html b/default/public/error/url-not-found.html
new file mode 100644
index 000000000..87974145f
--- /dev/null
+++ b/default/public/error/url-not-found.html
@@ -0,0 +1,15 @@
+<!DOCTYPE html>
+<html>
+
+<head>
+    <title>Not found</title>
+</head>
+
+<body>
+    <h1>Not found</h1>
+    <p>
+        The requested URL was not found on this server.
+    </p>
+</body>
+
+</html>
diff --git a/server.js b/server.js
index db7ba9306..bc2a884c2 100644
--- a/server.js
+++ b/server.js
@@ -615,6 +615,12 @@ app.use('/api/backends/scale-alt', scaleAltRouter);
 app.use('/api/speech', speechRouter);
 app.use('/api/azure', azureRouter);
 
+// If all other middlewares fail, send 404 error.
+const notFoundWebpage = fs.readFileSync('./public/error/url-not-found.html', { encoding: 'utf-8' });
+app.use((req, res, next) => {
+    res.status(404).send(notFoundWebpage);
+});
+
 const tavernUrlV6 = new URL(
     (cliArguments.ssl ? 'https://' : 'http://') +
     (listen ? '[::]' : '[::1]') +
