Windows 10 End of Support: What Happens to Office and Microsoft 365? Free Extension vs ESU Explained

Introduction

Windows 10 will officially reach the end of support on October 14, 2025.

While Microsoft has announced a one-year free Extended Security Updates (ESU) for some users, many believe this means they can continue using their PC exactly as before.

That’s not entirely true.

The free extension only covers critical security updates — no new features, no compatibility improvements, and no guarantee for continued full support for Microsoft 365 or Office.

In this article, we’ll break down:

• The difference between end of support, free extension, and paid ESU
• How Microsoft 365 and Office will be affected
• Real-world risks of staying on Windows 10
• Options to continue working safely

1. Understanding End of Support, Free Extension, and Paid ESU

Note: ESU—free or paid—does not restore new features or compatibility updates, and it does not extend official Microsoft 365 support on unsupported OS versions.

⚠ Important: Whether free or paid, ESUs are security-only. They do not extend Microsoft 365 or Office’s official support policy.

2. Impact on Microsoft 365

Microsoft 365 apps (Word, Excel, Outlook, etc.) are officially supported only on operating systems still within Microsoft’s support lifecycle.

• After Oct 14, 2025: Microsoft 365 won’t immediately stop working on Windows 10, but…
  • Feature updates will stop
  • Security patches for Microsoft 365 apps may end within months
  • Cloud sign-ins could fail in the future due to new encryption or authentication requirements

Bottom line: Expect gradual degradation in compatibility and security.

3. Impact on Office Perpetual Versions

Office 2019, 2021, and earlier may continue to run after Windows 10 support ends, but with risks:

• No security updates (macro-based malware risk increases)
• Newer file formats may not open correctly
• Outlook could stop connecting if server authentication changes
• OneDrive sync errors may occur

4. Real-World Issues You Might Face

• Outlook can’t send or receive emails due to unsupported authentication
• OneDrive sync stops because of outdated encryption protocols
• Teams/SharePoint access denied on older browsers
• File corruption when opening files from newer Office versions

5. Supported OS and Office/Microsoft 365 Timeline

Note: Support timelines are based on Microsoft’s official lifecycle policies as of August 2025 and may change in future updates.

6. If You Still Plan to Use Windows 10

Risks:

1. Higher malware infection rates
2. New hardware/software incompatibility
3. Cloud login failures
4. Gradual loss of functionality

Mitigation Tips:

• Use offline mode as much as possible
• Regularly back up files to an external drive
• 0Use a security suite for basic protection
• Avoid handling sensitive information

7. Safer Options

1. Upgrade to Windows 11 (or newer hardware if required)
2. Run Microsoft 365 on a supported OS (Windows 11/macOS/Linux via web apps)
3. Consider Office alternatives (LibreOffice, Google Docs)

8. Final Thoughts

End of support doesn’t mean your PC will instantly stop working — but it does mean Microsoft stops protecting it.

Free ESU gives you breathing room for one year, but it’s not a full extension of Microsoft 365 or Office support.

Plan your move now to avoid downtime, security risks, and compatibility headaches later.

✔️You might also find these helpful:

▶︎Windows 11 24H2 Update: Complete Troubleshooting & Upgrade Guide

▶︎App Disappeared After Windows Upgrade? Here’s Why and How to Get It Back

▶︎How to Upgrade to Windows 11 Without Internet — Complete Offline Guide

タグ: OS Upgrade, Windows 10, Microsoft 365, Free ESU, Security Updates, productivity tools, End of support, Office 2021, Office 2019, Paid ESU