Two subscriptions

Copy the Hotmail OneDrive files to your Windows PC, switch the OneDrive desktop app to the Yahoo account, and then upload the local copies; the two Microsoft accounts cannot be merged, and OneDrive supports only one personal account in its desktop sync app at a time.^1^^2^

1. Download the Hotmail files

Ensure the PC or an attached drive has at least 60–70 GB of free space.

1. Sign in to OneDrive with the Hotmail account.
2. Open File Explorer, right-click the Hotmail OneDrive folder, and select Always keep on this device.
3. Wait until the files show green check marks rather than blue cloud icons. “Always keep on this device” downloads the actual files instead of leaving online-only placeholders.^3^
4. Copy the downloaded folder to a separate ordinary folder, such as C:\OneDrive-Transfer. Use Copy/Paste, not Cut/Move, so the source remains intact.
5. Open several copied documents and photos to confirm they work.

Because the Hotmail account is over quota, it cannot upload, edit, or sync new files, but its existing files remain downloadable and read-only.^4^

If desktop downloading does not work, download folders in manageable batches from OneDrive on the web. Avoid attempting the entire 50–60 GB as one browser download.

2. Switch OneDrive to the Yahoo account

After confirming the local copy:

1. Select the OneDrive cloud icon in the Windows notification area.
2. Select Help & Settings → Settings → Account.
3. Select Unlink this PC → Unlink account.
4. Start OneDrive again from the Windows Start menu.
5. Sign in with the Yahoo-address Microsoft account that owns the active Microsoft 365 Family subscription.

Unlinking does not delete cloud data from the Hotmail account.^5^

3. Upload and verify the files

1. Open the new Yahoo OneDrive folder in File Explorer.
2. Create a folder such as Transferred from Hotmail.
3. Copy and paste the contents of C:\OneDrive-Transfer into that folder.
4. Keep the PC powered on and connected while OneDrive uploads.
5. Wait until the transfer folder shows green check marks and OneDrive reports that syncing is complete.
6. Sign in to the Yahoo OneDrive on the web and verify:
   • The expected top-level folders are present.
   • The approximate file count and size are reasonable.
   • A sample of documents, photos, and large files opens correctly.

For large quantities of files, Microsoft recommends the desktop app rather than the website’s Upload button.^6^

Do not delete the source yet

Keep both the Hotmail files and the local transfer copy until the Yahoo OneDrive has been fully verified. An over-quota personal OneDrive can be frozen after three months, and Microsoft might delete it and its files after six months, so complete the transfer promptly.^4^

After verification, the local transfer copy can be removed if no longer needed. The Hotmail Microsoft account does not need to be closed merely to stop using its OneDrive; closing it could also affect Hotmail email and other data tied to that account.

References

1. How to merge two accounts that have different email addresses...one personal and one family account - Microsoft Q&A
2. How do I merge my OneDrive for home with my OneDrive for work or school? | Microsoft Support
3. Save disk space with OneDrive Files On-Demand for Windows | Microsoft Support
4. My OneDrive says it's full
5. How to remove an account in OneDrive | Microsoft Support
6. Upload photos and files to OneDrive | Microsoft Support