diff --git a/src/network/html/FilesPage.html b/src/network/html/FilesPage.html
index 1721faa3..94ec65b3 100644
--- a/src/network/html/FilesPage.html
+++ b/src/network/html/FilesPage.html
@@ -818,7 +818,7 @@
 let failedUploadsGlobal = [];
 let wsConnection = null;
 const WS_PORT = 81;
-const WS_CHUNK_SIZE = 16384; // 16KB chunks for WebSocket - larger = faster
+const WS_CHUNK_SIZE = 4096; // 4KB chunks - smaller for ESP32 stability
 
 // Get WebSocket URL based on current page location
 function getWsUrl() {
@@ -831,6 +831,9 @@ function uploadFileWebSocket(file, onProgress, onComplete, onError) {
   return new Promise((resolve, reject) => {
     const ws = new WebSocket(getWsUrl());
     let uploadStarted = false;
+    let sendingChunks = false;
+
+    ws.binaryType = 'arraybuffer';
 
     ws.onopen = function() {
       console.log('[WS] Connected, starting upload:', file.name);
@@ -838,15 +841,53 @@ function uploadFileWebSocket(file, onProgress, onComplete, onError) {
       ws.send(`START:${file.name}:${file.size}:${currentPath}`);
     };
 
-    ws.onmessage = function(event) {
+    ws.onmessage = async function(event) {
       const msg = event.data;
       console.log('[WS] Message:', msg);
 
       if (msg === 'READY') {
         uploadStarted = true;
-        // Start sending binary data in chunks
-        sendFileChunks(ws, file, onProgress);
+        sendingChunks = true;
+
+        // Small delay to let connection stabilize
+        await new Promise(r => setTimeout(r, 50));
+
+        try {
+          // Send file in chunks
+          const totalSize = file.size;
+          let offset = 0;
+
+          while (offset < totalSize && ws.readyState === WebSocket.OPEN) {
+            const chunkSize = Math.min(WS_CHUNK_SIZE, totalSize - offset);
+            const chunk = file.slice(offset, offset + chunkSize);
+            const buffer = await chunk.arrayBuffer();
+
+            // Wait for buffer to clear - more aggressive backpressure
+            while (ws.bufferedAmount > WS_CHUNK_SIZE * 2 && ws.readyState === WebSocket.OPEN) {
+              await new Promise(r => setTimeout(r, 5));
+            }
+
+            if (ws.readyState !== WebSocket.OPEN) {
+              throw new Error('WebSocket closed during upload');
+            }
+
+            ws.send(buffer);
+            offset += chunkSize;
+
+            // Update local progress
+            if (onProgress) onProgress(offset, totalSize);
+          }
+
+          sendingChunks = false;
+          console.log('[WS] All chunks sent, waiting for DONE');
+        } catch (err) {
+          console.error('[WS] Error sending chunks:', err);
+          sendingChunks = false;
+          ws.close();
+          reject(err);
+        }
       } else if (msg.startsWith('PROGRESS:')) {
+        // Server confirmed progress - we can use this for accurate tracking
         const parts = msg.split(':');
         const received = parseInt(parts[1]);
         const total = parseInt(parts[2]);
@@ -866,39 +907,21 @@ function uploadFileWebSocket(file, onProgress, onComplete, onError) {
     ws.onerror = function(event) {
       console.error('[WS] Error:', event);
       if (!uploadStarted) {
-        // WebSocket connection failed, reject to trigger fallback
         reject(new Error('WebSocket connection failed'));
+      } else if (!sendingChunks) {
+        reject(new Error('WebSocket error during upload'));
       }
     };
 
-    ws.onclose = function() {
-      console.log('[WS] Connection closed');
+    ws.onclose = function(event) {
+      console.log('[WS] Connection closed, code:', event.code, 'reason:', event.reason);
+      if (sendingChunks) {
+        reject(new Error('WebSocket closed unexpectedly'));
+      }
     };
   });
 }
 
-// Send file in chunks via WebSocket
-async function sendFileChunks(ws, file, onProgress) {
-  const totalSize = file.size;
-  let offset = 0;
-
-  while (offset < totalSize) {
-    const chunk = file.slice(offset, offset + WS_CHUNK_SIZE);
-    const buffer = await chunk.arrayBuffer();
-
-    // Wait for buffer to clear if needed
-    while (ws.bufferedAmount > WS_CHUNK_SIZE * 4) {
-      await new Promise(r => setTimeout(r, 10));
-    }
-
-    ws.send(buffer);
-    offset += chunk.size;
-
-    // Update local progress (server will confirm)
-    if (onProgress) onProgress(offset, totalSize);
-  }
-}
-
 // Upload file via HTTP (fallback method)
 function uploadFileHTTP(file, onProgress, onComplete, onError) {
   return new Promise((resolve, reject) => {