Copilot Chat File Upload Stuck on Scanning: Fix

You try to upload a document in Copilot Chat, but the process stops at the scanning stage. The progress bar fills partway and then freezes. This happens most often with PDFs, Word documents, or images that contain sensitive or complex content. The root cause is the security scanning service that Copilot uses to inspect files before processing them. This article explains why the scan gets stuck and provides five tested fixes to get your uploads moving again.

Why the File Scan Gets Stuck in Copilot Chat

When you upload a file to Copilot Chat, the service sends the file to Microsoft’s secure content processing pipeline. This pipeline performs a threat scan, checks for malware, and extracts text for grounding. The scan uses Microsoft Defender for Office 365 and the Microsoft Graph data connectivity services. If the file contains embedded macros, large images, or encrypted sections, the scan can take longer than the 30-second timeout that the chat interface allows. The upload then appears stuck at the scanning stage even though the backend may still be processing.

Another common cause is a network interruption during the upload. Copilot Chat uses a chunked upload protocol. If your network drops even one packet, the scan cannot complete and the progress bar freezes. Browser extensions, especially ad blockers or script blockers, can also interfere with the scanning web socket connection.

File Format and Content Triggers

Certain file types are more likely to trigger a stuck scan. Files with embedded ActiveX controls, OLE objects, or password-protected sections force the scanner to attempt deep inspection. The scanner cannot read encrypted content, so it may time out. PDFs with more than 500 pages or Word files with dozens of embedded images also slow the scan past the timeout threshold.

Tenant Policy Restrictions

Your Microsoft 365 tenant administrator may have set data loss prevention policies that require additional scanning steps. If the file contains credit card numbers, social security numbers, or other sensitive data types, the policy forces a deep content inspection. This extra step can cause the scanning indicator to appear stuck for up to 60 seconds.

Steps to Fix a Stuck File Upload Scan

Try the fixes below in the order they appear. Test after each fix before moving to the next.

Fix 1: Reduce File Size and Remove Embedded Objects

1. Open the file in its native application
   For a Word document, open it in Microsoft Word. For a PDF, open it in Adobe Acrobat or a browser.
2. Remove embedded media and macros
   Delete any embedded videos, audio clips, or OLE objects. Remove all macros by going to File > Options > Trust Center > Trust Center Settings > Macro Settings and selecting “Disable all macros without notification.” Then save the file.
3. Compress images
   In Word, select an image and click Picture Format > Compress Pictures. Choose the “Email (96 ppi)” resolution. Apply to all images in the document.
4. Save a copy and reduce file size
   Use File > Save As and choose a new name. This removes residual metadata. If the file is larger than 25 MB, split it into multiple smaller files.
5. Upload the cleaned file to Copilot Chat
   Drag and drop the file or use the attachment icon. Wait 30 seconds. If the scan completes, the fix worked.

Fix 2: Clear Browser Cache and Cookies

1. Open your browser settings
   In Microsoft Edge, click the three-dot menu and select Settings. In Google Chrome, click the three-dot menu and select Settings.
2. Go to Privacy, search, and services
   In Edge, select Privacy, search, and services. In Chrome, select Privacy and security.
3. Clear browsing data
   Click “Choose what to clear.” Set the time range to “All time.” Check the boxes for “Cookies and other site data” and “Cached images and files.” Click Clear now.
4. Close and reopen the browser
   Navigate to copilot.cloud.microsoft and sign in again. Attempt the file upload.

Fix 3: Disable Browser Extensions Temporarily

1. Open the extensions management page
   In Edge, type edge://extensions in the address bar. In Chrome, type chrome://extensions.
2. Turn off all extensions
   Toggle the switch on each extension to the off position. Do not uninstall them.
3. Restart the browser
   Close all browser windows and reopen the browser. Go to Copilot Chat and upload the file again.
4. Re-enable extensions one by one
   If the upload works, turn extensions back on one at a time and test after each. The extension that breaks the upload is the culprit. Keep that extension off while using Copilot Chat.

Fix 4: Check Network Proxy and Firewall Settings

1. Contact your IT administrator
   If you use a corporate network, your proxy or firewall may block the scanning service. Ask your IT team to add the following domains to the allowlist: m365.cloud.microsoft, copilot.microsoft.com, graph.microsoft.com, and all subdomains. Also allow the TCP port 443 for HTTPS traffic.
2. Test on a different network
   If you are on a corporate network, disconnect from the VPN or use a personal hotspot. Upload the file again. If it works, the corporate network is the issue.
3. Disable network security software temporarily
   Turn off your local antivirus or firewall for 60 seconds and attempt the upload. If the scan completes, add Copilot Chat to the software’s exception list.

Fix 5: Use the Copilot App Instead of the Browser

1. Download the Copilot app
   Go to the Microsoft Store on Windows 11 or Windows 10 and search for “Copilot.” Install the official Microsoft Copilot app.
2. Sign in with your Microsoft 365 work or school account
   Open the app and sign in using the same account you use in the browser.
3. Upload the file through the app
   Click the file attachment icon in the chat input area. Select the file that was stuck in the browser. The app uses a different upload pipeline that may bypass the scanning timeout.

If Copilot Chat Still Shows Scanning After These Fixes

Copilot Returns No Output After the Scan Completes

If the scan indicator disappears but Copilot does not respond, the file may have failed the content extraction step. Open the file in its native application and save it as a plain text file. Upload the .txt version instead. Copilot can process plain text files faster and with fewer scanning errors.

Upload Works for Some File Types but Not Others

Copilot Chat supports .txt, .pdf, .docx, .xlsx, .pptx, and .csv files. If you are trying to upload a .zip, .exe, or .iso file, those formats are blocked by the scanning service. Convert the content to a supported format. For example, extract a text file from a .zip archive and upload the .txt file.

Scan Stuck on All Files, Even Small Ones

This indicates a tenant-wide or account-level issue. Sign out of Copilot Chat and sign back in. If the problem persists, contact your Microsoft 365 administrator. They can check the service health dashboard for Copilot-related incidents. They can also reset your Copilot data sources in the Microsoft 365 admin center under Settings > Copilot > Data sources.

Copilot Chat Browser vs Copilot App: File Upload Comparison

Item	Browser Version	Copilot App (Windows)
File size limit	25 MB	50 MB
Scanning timeout	30 seconds	60 seconds
Proxy bypass	Depends on browser proxy settings	Uses system proxy settings
Extension interference	Yes, extensions can block the scan	No browser extensions
Supported file types	.txt, .pdf, .docx, .xlsx, .pptx, .csv	Same, plus .rtf and .odt

If the browser version keeps getting stuck, switch to the Copilot app for a more reliable upload experience. The app gives you a longer scanning window and a higher file size limit.

You can now fix a stuck file upload scan in Copilot Chat by reducing file complexity, clearing browser data, or switching to the Copilot app. Start with the file cleanup steps because they address the most common cause. If you manage multiple users, ask your IT team to whitelist the Microsoft Graph endpoints in your proxy. For persistent issues, the Copilot app provides a fallback that avoids browser-specific scanning timeouts.