Copilot Chat Says File Type Not Supported: Fix

When you upload a file to Copilot Chat, you may see an error message stating the file type is not supported. This error prevents Copilot from reading or processing the file content. The cause is typically a file format that Copilot cannot parse, such as a binary format, an unsupported extension, or a corrupted file. This article explains why Copilot rejects certain file types and provides step-by-step fixes to resolve the error.

Why Copilot Chat Rejects Certain File Types

Copilot Chat uses a content processing pipeline that extracts text from uploaded files. This pipeline supports a limited set of file formats because each format requires a specific parsing library. The supported formats are:

• Plain text files (.txt)
• PDF files (.pdf)
• Word documents (.docx)
• Excel spreadsheets (.xlsx)
• PowerPoint presentations (.pptx)

If you upload a file with a different extension, such as .rtf, .odt, .csv, .json, .html, .zip, or .exe, Copilot will return the file type not supported error. The error also occurs if the file extension is correct but the internal structure is corrupted or if the file is password-protected. Copilot cannot decrypt or repair files.

Technical Root Cause

The Copilot service runs on Microsoft Azure and uses Azure AI Document Intelligence and Microsoft Graph to extract text. These services only accept files with MIME types that match the supported list. When a file with an unsupported MIME type is uploaded, the service rejects it at the validation stage before any text extraction begins. This is a security measure to prevent malicious binary files from being processed.

Steps to Fix File Type Not Supported Error

1. Identify the actual file format
   Right-click the file in File Explorer and select Properties. Look at the Type of file field. If it says something other than the supported types, you must convert it. For example, a .doc file (Word 97-2003) is not supported — only .docx is supported.
2. Convert the file to a supported format
   Open the file in its native application. For Word, go to File > Save As and choose Word Document (.docx). For Excel, choose Excel Workbook (.xlsx). For a plain text file, rename the extension to .txt. If you do not have the native application, use a free online converter such as CloudConvert or Zamzar. Upload the file and select the target format. Download the converted file.
3. Check for file corruption
   If the file extension is correct but the error persists, the file may be corrupt. Try opening the file in its native application. If it fails to open or shows garbled content, the file is damaged. Recover an earlier version from a backup or recreate the file content manually.
4. Remove password protection
   Copilot cannot read password-protected files. Open the file in its application, go to File > Info > Protect Document, and remove the encryption password. Save the file again without a password.
5. Copy text to a plain text file
   If conversion is not possible, copy the text content from the unsupported file. Open the file in any text editor or viewer that can display the text. Select all text, copy it to the clipboard, paste it into Notepad, and save the file as a .txt file. Upload the .txt file to Copilot Chat.
6. Use Microsoft 365 apps to open the file first
   If the file is stored in OneDrive or SharePoint, open it in the corresponding Microsoft 365 web app. Then use the Copilot pane within that app to ask questions about the file. This bypasses the file upload limitation in Copilot Chat.

If Copilot Still Has Issues After the Main Fix

Copilot Chat Shows Error After File Conversion

If you converted a file but still see the error, the conversion tool may have produced a file with an incorrect internal format. Try a different converter. For example, if you used an online tool, use the native Microsoft Office application instead. Also verify that the file extension matches the actual format. Renaming a .csv file to .xlsx does not change the internal structure — you must perform a proper conversion.

Copilot Returns No Content After Upload

If the file uploads without an error but Copilot says it cannot find content, the file may contain only images, scanned pages, or embedded objects without selectable text. Copilot cannot extract text from images unless OCR is enabled. For PDFs, ensure the file is a text-based PDF, not a scanned image. Use a PDF OCR tool to convert scanned pages to text before uploading.

Copilot Chat Limits File Size

Even with a supported file type, Copilot Chat has a file size limit. For Copilot with Microsoft 365 commercial accounts, the limit is 3 MB per file. For Copilot Pro, the limit is 50 MB per file. If your file exceeds the limit, split it into smaller parts or remove large images and embedded media before uploading.

Item	Copilot Chat (Microsoft 365 Work)	Copilot Chat (Copilot Pro)
Maximum file size	3 MB	50 MB
Supported text formats	.txt, .pdf, .docx, .xlsx, .pptx	.txt, .pdf, .docx, .xlsx, .pptx
Image extraction from files	Not supported	Not supported
Password-protected files	Not supported	Not supported
Workaround for unsupported formats	Copy text to .txt or use Copilot in Office apps	Copy text to .txt or use Copilot in Office apps

Now you can identify the file format, convert it to a supported type, and upload it to Copilot Chat without the error. If you frequently work with unsupported file types, use the Copilot pane inside Word, Excel, or PowerPoint to access file content directly. As an advanced tip, you can enable the Microsoft Graph Data Connect feature in your tenant to allow Copilot to index and search across custom file formats stored in SharePoint, but this requires an administrator to configure the connector.