Copilot Chat Image Upload Fails With Network Error: Fix

You try to upload an image to Copilot Chat, but the upload fails with a network error. This can happen in Microsoft Edge, Chrome, or the Copilot mobile app. The root cause is often a blocked content delivery network, a proxy interference, or a browser extension that strips image metadata. This article explains why the error occurs and provides the exact steps to resolve it so you can upload screenshots, diagrams, and photos again.

Why Copilot Chat Rejects Image Uploads With a Network Error

Copilot Chat uses a dedicated content delivery network to handle image uploads. When you attach a file, the Copilot client sends a preflight request to cdn.copilot.microsoft.com. If that request is blocked by a corporate proxy, a VPN rule, or a browser extension, the upload fails immediately with a network error. The error message does not specify which resource was blocked, so the fix requires checking each layer.

Another common cause is a corrupted local cache. The Copilot app stores temporary data for image preview and compression. If that cache is stale or damaged, the app cannot complete the upload handshake and returns a generic network error. The same symptom can appear when your internet connection drops briefly during the upload, but most users report the error even on stable connections.

A less frequent but possible cause is an expired authentication token. Copilot Chat requires a valid Microsoft 365 or Microsoft account token to authorize the upload endpoint. If your token has expired and the app fails to refresh it silently, the upload is rejected as a network error rather than an authentication error.

Steps to Re-enable Image Uploads in Copilot Chat

Follow these methods in order. Test an image upload after each method to see if the error is resolved.

Method 1: Allow the Copilot CDN in Your Firewall or Proxy

1. Open your corporate firewall or proxy management console
   If you are on a work or school network, contact your IT administrator. Provide the exact URL to allow: cdn.copilot.microsoft.com and all subdomains. Also allow copilot.microsoft.com for the main service.
2. Check the VPN split-tunnel configuration
   If you use a VPN, open the VPN client settings and add cdn.copilot.microsoft.com to the split-tunnel bypass list so traffic to that domain does not go through the VPN tunnel.
3. Test the upload
   Open Copilot Chat in your browser. Drag and drop a JPG file under 20 MB. If the upload succeeds, the CDN block was the cause.

Method 2: Disable Browser Extensions That Block Content

1. Open your browser extension manager
   In Microsoft Edge, click the puzzle icon in the toolbar and select Manage extensions. In Chrome, click the three-dot menu > Extensions > Manage Extensions.
2. Disable ad blockers and privacy extensions
   Turn off uBlock Origin, AdBlock Plus, Privacy Badger, Ghostery, and similar extensions temporarily. Do not disable password managers or accessibility tools.
3. Reload Copilot Chat
   Press F5 to refresh the tab. Try uploading an image again.
4. Re-enable extensions one by one
   If the upload works with extensions off, turn each extension back on and test until you find the one causing the block. Leave that extension disabled for Copilot Chat or add an exception rule.

Method 3: Clear the Copilot App Cache on Windows 11

1. Open Windows Settings
   Press Windows key + I to open Settings.
2. Go to Apps > Installed apps
   Scroll to Microsoft Copilot or Copilot. Click the three-dot menu and select Advanced options.
3. Click Reset
   Under the Reset section, click the Reset button. This clears the app cache and resets the app to its default state. Your account sign-in is preserved.
4. Restart the Copilot app
   Close and reopen Copilot. Sign in again if prompted. Test the image upload.

Method 4: Refresh Your Microsoft Account Token

1. Sign out of all Microsoft services
   In Copilot Chat, click your profile picture and select Sign out. Do the same in the browser at account.microsoft.com.
2. Clear browser cookies for Microsoft domains
   Open your browser settings. Search for cookies and site data. Remove all cookies for microsoft.com, live.com, and copilot.microsoft.com.
3. Sign back in
   Go to copilot.microsoft.com and sign in with your Microsoft 365 or personal Microsoft account. Try uploading an image.

If Copilot Chat Still Fails to Upload Images

Copilot Returns a Different Error Code: 400 or 413

A 400 error means the file format is not supported. Copilot Chat accepts JPG, PNG, GIF, BMP, and WEBP. Convert the file to one of these formats and try again. A 413 error means the file is too large. The maximum file size is 20 MB. Reduce the image resolution or compress it before uploading.

Copilot Uploads the Image but Does Not Process It

If the upload completes but Copilot does not analyze the image, the file may be corrupted. Open the image in a photo viewer to confirm it displays correctly. Re-save the image using a tool like Paint or Photos and re-upload. Another cause is a missing file extension. Rename the file to include the correct extension, for example photo.jpg instead of photo.

Copilot Mobile App Image Upload Fails on iOS or Android

On mobile, network errors often come from a weak Wi-Fi signal or a cellular data restriction. Open your phone Settings > Copilot > Cellular Data and ensure cellular data is enabled. On iOS, go to Settings > Copilot > Photos and set access to Read and Write. On Android, go to Settings > Apps > Copilot > Permissions and enable Storage. Finally, restart the mobile app.

Copilot Chat Image Upload: Browser vs Mobile App Comparison

Item	Browser (copilot.microsoft.com)	Copilot Mobile App
Max file size	20 MB	20 MB
Supported formats	JPG, PNG, GIF, BMP, WEBP	JPG, PNG, GIF, BMP, WEBP
Primary network error cause	CDN blocked by proxy or extension	Cellular data restriction or weak signal
Cache clear location	Browser settings > Cookies and site data	App Settings > Storage > Clear cache
Authentication refresh	Sign out and clear cookies	Sign out in app settings

Both platforms use the same CDN and file size limits. The browser version is more susceptible to extension interference, while the mobile app is more sensitive to network connectivity and permission settings.

You can now identify the exact cause of the network error and apply the matching fix. Start with the CDN allowlist if you are on a corporate network. Disable ad blockers next. If the issue persists, clear the app cache or refresh your Microsoft account token. For recurring problems, set a browser exception for cdn.copilot.microsoft.com in your ad blocker to prevent future blocks.