Microsoft 365 Copilot Mobile Now Uploads Local Files to OneDrive by Default

Microsoft is testing Copilot Tasks, but recent mobile changes are raising concerns. A new update shifts Microsoft 365 Copilot toward a Copilot-first experience instead of a traditional document viewer.

According to Windows Latest, Microsoft has modified how Microsoft 365 Copilot works on Android and iOS devices. The app now routes opened files directly into Copilot chat rather than launching a standard file preview.

Copilot chat replaces the traditional viewer

Previously known as the Office Hub, the app later became Microsoft 365 and was rebranded again in 2025 as Microsoft 365 Copilot. Over time, Microsoft steadily reduced emphasis on document viewing and increased Copilot integration.

In October 2025, Microsoft already placed the document viewer behind additional taps. A recent update goes further by launching Copilot chat immediately when users open a file.

Microsoft says this design enables instant summaries and quicker file access through conversational prompts. However, real-world tests show a more complex workflow.

Local files are uploaded to OneDrive before analysis

When users open a local document, the app uploads the file to Microsoft OneDrive before Copilot analyzes it. Only after syncing does Copilot attempt to search and summarize the content.

If Copilot fails to process the file, the document may not load at all. In some cases, Copilot reportedly references unrelated OneDrive documents instead of the intended file.

Files already synced with OneDrive continue to open more normally. Unsynced local files, however, require a full upload before access becomes possible.

Viewer access is now hidden inside Copilot

The traditional document viewer has not disappeared entirely, but Microsoft has moved it inside Copilot’s references tab. Users must navigate through Copilot chat to reach the actual document preview.

If the upload or AI processing fails, the file may not appear inside the app. Some users may need to manually upload documents to OneDrive before accessing them through Copilot.

Microsoft suggests using standalone Office apps such as Microsoft Word, Microsoft Excel, and Microsoft PowerPoint for standard file viewing without AI routing.

Copilot-first strategy raises privacy questions

The update effectively transforms the mobile app into a Copilot-centric interface. While Microsoft promotes productivity benefits, critics argue that automatic uploads and AI processing introduce new friction and potential privacy risks.

The concerns arrive shortly after Microsoft acknowledged a Copilot bug that summarized confidential emails without user awareness. Some policymakers have reacted strongly to rapid AI adoption, including restrictions on AI usage within certain government environments.

Microsoft continues testing Copilot Tasks and expanding Copilot features across its ecosystem. Whether users embrace this AI-first direction on mobile may depend on how smoothly file handling and privacy safeguards evolve in future updates.