Quick answer. As of September 2026, move every machine that can reach the internet at least once every 30 days to Microsoft 365 Apps, which Microsoft recommends, and put machines that cannot take feature updates or cannot connect to the internet on Office LTSC 2024, the path Microsoft Learn gives for commercial customers not yet ready for the cloud. Office LTSC 2024, according to Microsoft, gets five years of Mainstream Support and no Extended Support, receives no new features, and is supported for connecting to Microsoft 365 services until October 9, 2029. Office LTSC 2021 and Office 2021 reach end of support on October 13, 2026, after which, according to Microsoft, there will be no technical support, bug fixes, or security updates for them, and Office LTSC 2021 will no longer be supported for connecting to Microsoft 365 services.
When Microsoft Learn’s end-of-support notice for Office LTSC 2021 reaches your desk, the inventory behind it can turn up copies nobody tracked: a disconnected enclave, instrument PCs in a lab, a production line, shared clinical workstations, kiosks. Moving everyone to Microsoft 365 Apps puts an offline machine at risk of losing editing, and buying the fixed release again keeps connected users on software with no new features and a connectivity end date. This guide sets out what Microsoft’s own pages, read on 2026-09-24, say about each choice, so every class of machine gets an assignment you can defend. It covers Office on Windows machines; Mac editions are outside it.
What Ends on October 13, 2026, and What Keeps Running Until Then
If the notice on your desk names only Office LTSC 2021, check the retail copies as well, because both end the same day. Microsoft’s announcement Office LTSC 2021 reaching end of support on October 13, 2026 states: “Office LTSC 2021 will reach end of support on October 13, 2026.” It continues: “After this date, Microsoft will no longer provide technical support, bug fixes, or security updates for this product.” and “This may increase your organization’s exposure to security risks and could impact compliance requirements.”
Microsoft’s Ending Support in 2026 page lists Office 2021 among “The following products, governed by the Modern Policy, will retire in 2026.” and Office LTSC 2021 among “The following products and releases, governed by the Fixed Policy, will end support in 2026.” Both rows carry October 13, 2026. The same rows name the 2021 editions of Access, Excel, OneNote, Outlook, PowerPoint, Project, Publisher, Visio and Word, and the Fixed Policy row also names Skype for Business LTSC 2021. On what retirement means, that page says: “Upon retirement or end of support, there will be no new security updates, non-security updates, free or paid assisted support options or online technical content updates.”
If Office LTSC 2021 still connects to Exchange Online or SharePoint Online after that date, the connection is unsupported. Microsoft’s Office versions and connectivity to Microsoft 365 services table lists Office LTSC 2021 as supported for connecting until October 13, 2026, and the page adds: “Older Office versions might still be able to connect to Microsoft 365 services, but that connectivity isn’t supported.” Its lists for Project and Visio give “Project Professional 2021 and Project Standard 2021 (until October 2026)” and “Visio LTSC Professional 2021 and Visio LTSC Standard 2021 (until October 2026)”.
There is no Extended Support to plan around. Microsoft’s Overview of Office LTSC 2021 says no Extended Support will be available for these products after their five years of Mainstream Support end. Until the date, Microsoft’s Update history for Office LTSC 2021 and Office 2021 page says “Microsoft releases security and quality updates for Office LTSC 2021 (volume licensed) and Office 2021 (retail).”
Sort the Estate by Machine Class Before You Choose an Edition
If you pick the edition before you know the machines, the offline ones end up on the wrong product. Build the inventory first, and record every copy of the retiring Office editions against three questions, in this order:
- Can the machine reach the internet at least once every 30 days? Microsoft’s Overview of licensing and activation in Microsoft 365 Apps ties Microsoft 365 Apps staying fully functional to this check.
- Can the machine take feature updates, or does it run a regulated or tested workload that cannot change without revalidation?
- Is the machine used by one named person, or is it shared or non-interactive?
The answers decide whether each machine gets Office LTSC 2024 or Microsoft 365 Apps. Connected, single-user desktops that can take feature updates go to Microsoft 365 Apps. Machines that cannot take feature updates or cannot connect go to Office LTSC 2024, which Microsoft’s Plan an upgrade from older versions of Office to Microsoft 365 Apps page describes this way: “Office LTSC 2024 is designed for specific scenarios. These include regulated devices that can’t accept feature updates, process control devices on manufacturing floors, and specialty systems that can’t connect to the internet.” Machines that are offline for a while but not for good need the offline test in the section below before they are assigned. Put the class, the owner of the machine and the assigned edition in the same register row, so the decision can be read back later. The Windows layer on the same desktops has its own date, and Windows 11 23H2 End of Updates and WSUS covers the feature-update path and update channel for devices whose updates end on November 10, 2026.
Connected User Desktops: Microsoft 365 Apps
When a desktop is online every day and used by one person, Microsoft’s own answer is Microsoft 365 Apps. The Office LTSC 2021 reaching end of support on October 13, 2026 announcement says: “To remain in a supported environment, begin upgrading to Microsoft 365 Apps now.” Microsoft’s Office versions and connectivity to Microsoft 365 services page adds: “The most up-to-date subscription versions of the Office client are always supported connecting to Microsoft 365 services.”
The trade is a moving target. Microsoft’s Plan an upgrade from older versions of Office to Microsoft 365 Apps page says: “A key difference between Microsoft 365 Apps and Office LTSC is that Microsoft 365 Apps is continuously updated, with new features released as frequently as monthly.” The other side of that trade is in Overview of Office LTSC 2024: “Office LTSC 2024 doesn’t include the latest cloud-backed features and functionality available in Microsoft 365 Apps.”
For desktops that need testing before features change, choose the update channel deliberately. Microsoft’s Overview of update channels for Microsoft 365 Apps describes Semi-Annual Enterprise Channel as “For non-interactive devices and those running specialized or business-critical workloads that require extensive testing before new Microsoft 365 Apps features are implemented.” The same page, last updated May 2026, says: “Beginning July 2026, Semi-Annual Enterprise Channel will begin receiving monthly feature and security updates.” Plan the test cycle around that change rather than around the older twice-a-year pattern.
Two more cases sit in this class. For a desktop still on Windows 10, Microsoft’s Windows 10 end of support and Microsoft 365 Apps page says: “Microsoft will continue providing security updates for Microsoft 365 Apps on Windows 10 for three years after Windows 10 reaches end of support. These updates will be delivered through the standard update channels, ending on October 10, 2028.” The Windows decision for those devices is a separate one, and this guide does not make it. For a shared desktop or kiosk, Microsoft’s Device-based licensing for Microsoft 365 Apps for enterprise page says: “Commercial customers can use Microsoft 365 Apps for enterprise (device) to assign a Microsoft 365 Apps for enterprise license to a Windows client device instead of to a user.”
Machines That Cannot Take Feature Updates or Cannot Connect: Office LTSC 2024
If a machine runs a validated instrument, a production line or a system that never sees the internet, Microsoft 365 Apps is the wrong fit, and Microsoft names the fixed release for it. Its announcement says: “For organizations that are not yet ready to move to the cloud, the recommended upgrade path is to the most recent supported on premises version for commercial customers, Office LTSC 2024.” Microsoft’s Overview of Office LTSC 2024 describes it as “the most recent edition of Microsoft’s core productivity apps designed for use in highly regulated or restricted environments that can’t take feature updates.” Its Plan an upgrade from older versions of Office to Microsoft 365 Apps page describes how it is sold: “Office Long Term Service Channel (LTSC) 2024, which is sold as a one-time purchase through a volume license agreement, and available for one device per license.”
Know what the fixed release does not give you. The Overview of Office LTSC 2024 states: “Office LTSC 2024, including Project and Visio, receive five years of Mainstream Support. After this period, there will be no Extended Support for these products.” and “Keep in mind that Office LTSC 2024 doesn’t receive any new features.” Microsoft lists Office LTSC 2024 as supported for connecting to Microsoft 365 services until October 9, 2029.
Installation, and activation through KMS, work without an internet connection. The same Overview of Office LTSC 2024 says installation needs no internet connection once the installation files are downloaded, and adds: “Internet connectivity is required for MAK activation, but not for KMS activation.” Its list of supported operating systems includes Windows 11, Windows 11 LTSC 2024, Windows 10 LTSC 2021 and Windows 10 LTSC 2019; which Windows edition a fixed-function machine runs is a separate decision, and this guide does not make it.
Before the rollout, write down what changes. From the Overview of Office LTSC 2024, with an owner beside each item:
- Publisher: Microsoft Learn says “Microsoft Publisher is not included with Office LTSC 2024. This change is due to the planned retirement of Publisher, which will no longer be supported after October 2026.”
- Teams: Microsoft Learn says “The Microsoft Teams app isn’t preinstalled with Office LTSC 2024, but is available as a separate download.”
- ActiveX: Microsoft Learn says “In Office LTSC 2024, ActiveX controls are disabled by default. However, IT administrators can re-enable ActiveX where necessary.”
- Excel: Microsoft Learn says “The Publish to Power BI feature is removed from Excel.”
- Access: Microsoft Learn says “Office LTSC Professional Plus 2024 includes Access, Excel, OneNote, Outlook, PowerPoint, and Word.” Retiring the Access databases themselves is a separate project from this one.
On add-ins, the Overview of Office LTSC 2024 says: “Add-ins and other extensibility solutions compatible with Office LTSC 2021 or Office 2019 are likely to work with Office LTSC 2024, requiring minimal testing.” Likely is not certain, so test the add-ins each machine class depends on before the cutover. On sequence, it says: “Uninstall versions of Office before deploying Office LTSC 2024.” For the deployment tooling across a managed fleet, i3solutions stands up Intune endpoint management as project work, described in Microsoft Intune Technology Readiness Services.
The Machine That Is Offline for a While, Not for Good
If a machine drops off the network for a field deployment, a closed room or a maintenance window, the question is how long it stays off. Microsoft’s Overview of licensing and activation in Microsoft 365 Apps states: “As long as the computer can connect to the internet at least once every 30 days, Microsoft 365 Apps remains fully functional. If the computer goes offline for more than 30 days, Microsoft 365 Apps enters reduced functionality mode until the next time a connection can be made.” It describes that mode: “In reduced functionality mode, Microsoft 365 Apps remains installed on the device, but users can only view and print their documents.” And for machines that never connect: “Because of its online activation features, Microsoft 365 Apps won’t work on computers that are completely cut off from the internet.”
There is a longer window, with a condition. Microsoft’s Overview of extended offline access for Microsoft 365 Apps says: “Extended offline access enables devices running Microsoft 365 Apps for enterprise to stay activated for up to six months without the need to connect to the internet to validate the license and install updates.” The same page says: “Extended offline access is included with specific license packages. To find out about eligibility for your organization, contact your Microsoft account representative.”
Decide by the longest time the machine is offline. Within Microsoft’s connection limit, Microsoft 365 Apps fits. Beyond it, confirm extended offline access eligibility in writing before assigning the machine to Microsoft 365 Apps on the strength of it. If the machine never connects, it goes to Office LTSC 2024.
Government Clouds: What Microsoft States and What It Leaves Open
If the tenant is in a US government cloud, start from what Microsoft publishes for government plans. Microsoft’s Office 365 Government service description lists Microsoft 365 Apps for enterprise as available in Office 365 Government G3 and G5 and not in G1 or F3, and its note on the Office applications reads: “Applications are fully available in the government clouds, with the exception of the specific features not available at this time.” Microsoft’s Office application and feature availability in Government plans page says: “The following Office applications are available in the government clouds; however, some cloud-based capabilities may not be currently available, as indicated in the table.” Check that table for the features your users rely on, per application and per cloud, before assigning a class to Microsoft 365 Apps.
Read the fixed-release recommendation with its condition. Microsoft’s announcement Office LTSC 2021 reaching end of support on October 13, 2026 recommends Office LTSC 2024 “for commercial customers”, and the pages this guide relies on do not say how Office LTSC 2024, extended offline access or device-based licensing apply in GCC High or DoD. Confirm each with Microsoft before planning on it.
Moving a tenant into GCC High is a different project, covered in Microsoft 365 GCC High Migration Checklist: Best Practices for Defense Contractors. i3solutions plans and runs GCC High migrations for regulated defense organizations, working alongside the customer’s AOS-G supplier, which provisions the tenant.
When This Is Not the Decision Yet
If the estate is not ready for the Office choice, forcing it early creates rework:
- If the operating system on the machine is itself past support, the Office choice waits on the platform. Testing whether that system is worth extending at all is covered in Are Our Current Systems Stable Enough to Extend, or Too Fragmented to Build On?, and the operating system decision is a separate one.
- If an equipment vendor has not tested its process-control machine with Office LTSC 2024, the words on Microsoft Learn about add-ins are “likely to work”, not certain. Test before the date, and record any copy left on 2021 after it as an accepted, documented risk with a named owner and an exit date.
- If Access databases on these machines should not survive the move, retiring them is its own project and does not belong inside the Office rollout.
- If the Office move is one line of a larger Microsoft program, its place in that program’s order is decided there, not here.
What to Ask of Whoever Does the Work
If you bring in outside help, judge the plan against these items:
- An inventory of every copy of the retiring Office editions, by machine class, with Microsoft’s connection limit for Microsoft 365 Apps applied to each.
- A written list of what changes on the fixed release (Publisher, Teams, ActiveX, Publish to Power BI), with an owner for each item.
- An activation plan per class: online activation for Microsoft 365 Apps, extended offline access only where eligibility is confirmed, and KMS or MAK for Office LTSC 2024.
- An update-channel choice for tested desktops, written against the Semi-Annual Enterprise Channel change.
- A named owner for any copy still on the retiring editions after Microsoft’s end-of-support date, recorded as an accepted risk.
- A plain statement of who runs the desktops and applies updates as an ongoing operation once the project closes.
- Senior, US-based people doing the work.
How i3solutions Answers
i3solutions plans and runs governed Azure and Microsoft 365 migrations with senior, U.S.-based engineers.
Delivery is senior and US-based. Deploying and configuring Microsoft 365 Apps and moving it onto a supported update channel is project work i3solutions does. Embedded specialists can also work inside your team. An i3solutions engagement does not produce managed-service ownership, a replacement for the internal team, open-ended scope expansion, or vendor lock-in. The wider practice is Microsoft Consulting Services Built for Enterprise Complexity.
Key Takeaways
- On Microsoft Learn, Office LTSC 2021 and Office 2021 reach end of support on October 13, 2026, and Office LTSC 2021 is supported for connecting to Microsoft 365 services until that date.
- On Microsoft Learn, Microsoft recommends Microsoft 365 Apps, and Office LTSC 2024 for commercial customers not yet ready for the cloud.
- On Microsoft Learn, Microsoft 365 Apps stays fully functional while the machine connects at least once every 30 days; extended offline access allows up to six months only where the organization’s license packages include it.
- On Microsoft Learn, Office LTSC 2024 has five years of Mainstream Support, no Extended Support, no new features, and connectivity to Microsoft 365 services until October 9, 2029.
- Sort the estate by machine class first: connected desktops, machines that cannot take feature updates, machines that cannot connect, and government tenants.
Frequently Asked Questions
When does support end for Office 2021 and Office LTSC 2021?
Microsoft Learn states: “Office LTSC 2021 will reach end of support on October 13, 2026.” For Office LTSC 2021, Microsoft Learn adds that after that date Microsoft “will no longer provide technical support, bug fixes, or security updates for this product.” Microsoft’s 2026 end-of-support list on Microsoft Learn puts Office 2021 under the Modern Policy on the same date.
Can Office LTSC 2021 still connect to Microsoft 365 after October 13, 2026?
Not with support. On Microsoft Learn, Microsoft lists Office LTSC 2021 as supported for connecting to Microsoft 365 services until October 13, 2026, and says: “Older Office versions might still be able to connect to Microsoft 365 services, but that connectivity isn’t supported.”
Should we move to Office LTSC 2024 or Microsoft 365 Apps?
Microsoft’s announcement says: “To remain in a supported environment, begin upgrading to Microsoft 365 Apps now.” and “For organizations that are not yet ready to move to the cloud, the recommended upgrade path is to the most recent supported on premises version for commercial customers, Office LTSC 2024.” Microsoft Learn adds that “Office LTSC 2024 is designed for specific scenarios. These include regulated devices that can’t accept feature updates, process control devices on manufacturing floors, and specialty systems that can’t connect to the internet.”
Does Microsoft 365 Apps work on machines that are offline?
For a limited time. Microsoft Learn says that “As long as the computer can connect to the internet at least once every 30 days, Microsoft 365 Apps remains fully functional.” Microsoft Learn adds that if the computer goes offline for more than 30 days, Microsoft 365 Apps “enters reduced functionality mode until the next time a connection can be made.” On Microsoft Learn, extended offline access allows up to six months, and Microsoft says that “Extended offline access is included with specific license packages. To find out about eligibility for your organization, contact your Microsoft account representative.”
How long is Office LTSC 2024 supported?
Microsoft Learn says that “Office LTSC 2024, including Project and Visio, receive five years of Mainstream Support. After this period, there will be no Extended Support for these products.” Microsoft Learn lists Office LTSC 2024 as supported for connecting to Microsoft 365 services until October 9, 2029.
Planning the Decision
If your estate needs each machine class assigned to Microsoft 365 Apps or Office LTSC 2024, with the activation and update-channel design to match, before October 13, 2026, the next step is a conversation about your machines.
