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Microsoft ended official support for WebRTC-based Teams optimization on Windows devices connecting to Citrix, Azure Virtual Desktop, and Windows 365 on October 1, 2026. Calls still connect, but Microsoft and Citrix no longer support that setup.
On April 1, 2027, WebRTC stops working on those devices. Teams will then use only the new VDI solution, built on a media engine called SlimCore. Any device that can’t run it will process calls on the virtual desktop itself.
If your team works on a hosted virtual desktop, this change has two owners. Part of it sits on the servers your provider manages, and part of it sits on the devices your users log in from.
What Is Changing in Teams Optimization on Virtual Desktops
Under the old setup, Teams handed audio and video to an engine built by each VDI vendor. On Citrix, that engine was HdxRtcEngine, and SlimCore now takes over that role. Teams could only offer the meeting features the vendor engine supported.
SlimCore is the same media engine that runs in the native Teams desktop app. A small plugin inside the Citrix Workspace app downloads SlimCore to the user’s device, and Microsoft updates it automatically with each new Teams version.
Because Microsoft owns the engine, Teams on a virtual desktop now supports features WebRTC never offered. The feature list for the new optimization includes 1080p video, the 7×7 gallery view, hardware acceleration on the user’s device, and QoS markings. Organizers and presenters of town halls are also optimized for the first time, and optimization for town hall attendees is in public preview for Windows devices.
More of the work now happens on the user’s device and network. A process called MsTeamsVdi.exe runs on the device and handles every network connection for calls and meetings.
Key Dates by Device and Platform
The deadline depends on the device your users connect from and the platform the desktop runs on.
| Device and platform | End of support | End of availability |
| Windows devices on Citrix, Azure Virtual Desktop, or Windows 365 | October 1, 2026 | April 1, 2027 |
| Mac devices on Citrix, Azure Virtual Desktop, or Windows 365 | April 1, 2027 | September 1, 2027 |
| Windows devices on Omnissa Horizon | July 1, 2027 | October 1, 2027 |
| Supported Linux thin clients | Not affected | Not affected |
| Teams in a web browser | Not optimized on either stack | Not optimized on either stack |
All dates come from Microsoft’s Teams for VDI requirements page.
Supported Linux thin clients from IGEL, Dell, HP, 10ZiG, and NComputing can keep their current optimization until Microsoft releases a version of the new solution for Linux. Offices running zero clients or Linux thin clients can keep using them through the deadline.
Teams in a web browser is a different case. Microsoft states that Teams for web isn’t supported inside VDI, so users should run the Teams desktop app inside their virtual desktop.
Check List
Citrix DaaS Deployment Preparation Checklist
What Happens When a Device Is Not Ready
After April 1, 2027, a Windows device that can’t load SlimCore falls into fallback mode. Teams then processes all audio and video on the virtual machine, a mode Microsoft calls server-side rendering, and the user experience degrades.
On a shared session desktop, that processing runs on the same host as other users’ applications. For unoptimized sessions, Microsoft notes high use of CPU, RAM, and virtual channel bandwidth on the virtual desktop.
Users get notice before the deadline. Two months before the end of availability, Teams shows a warning dialog. If the plugin is missing, the dialog tells users to download it from Microsoft.
What the Desktop Provider Handles on a Cloud-Hosted Desktop
Several requirements sit on the server side. On a cloud-hosted desktop, the provider owns them.
Virtual channels. SlimCore needs three custom Citrix virtual channels: MSTEAMS, MSTEAM1, and MSTEAM2. On Citrix VDA 2203 and later, the virtual channel allow list is on by default and blocks these channels until an admin adds them and reboots the VDAs. VDA 2603 and later allow the three channels by default. Ace Cloud Hosting desktops run Citrix VDA 2603 or later, so Teams can open these channels without extra policy work.
Teams version. Microsoft shows in-app alerts when a Teams version is more than 60 days old and blocks the app after 90 days. Non-persistent desktops with auto-update turned off need their image updated on a regular schedule.
Desktop operating system. Teams on VDI does not support Windows Server 2016 or 2019 as the desktop OS. Ace Cloud Hosting desktops run only Windows versions with active support.
A firm that runs its own Citrix environment handles each of these items itself. The minimum for SlimCore is VDA 2203 LTSR CU3 or 2305 CR, so older sites need an upgrade before April 2027. Citrix Studio policies for the legacy optimization also stop taking effect after the deadline.
With Managed Citrix DaaS solutions, VDA and Windows maintenance are part of the service. Your IT time can go to the devices, where the rest of the change happens. With desktop-as-a-service, your IT team does not plan or run these server upgrades.
Ace Cloud Hosting desktops run Citrix VDA 2603 or later, and our support team helps set up the Teams plugin on each device.
What Stays on Your Users’ Devices
Each device needs the following items, starting with the software every user needs.
Citrix Workspace app and the Teams plugin. Each Windows device needs a supported Citrix Workspace app with the Microsoft Teams VDI plugin installed. Citrix Workspace app for Windows 2402 LTSR or later can install the Teams VDI plugin during a fresh install, and in-place upgrades need version 2405 CR or later. From version 2508, the plugin option is selected by default. From version 2603, the Workspace app can update the plugin to the latest version on its own. The plugin must match the architecture of the Workspace app, and per-user installs of the Workspace app are not supported.
Microsoft’s October 2026 plugin release improves SlimCore downloads during network interruptions and reduces install failures caused by antivirus scans. Ace Cloud Hosting support helps users install the Workspace app and the plugin on their own devices.
Device hardware. Microsoft’s minimum is Windows 10 version 1809, a four-core Intel Celeron at 1.10 GHz or equivalent, and 4 GB of RAM. Older two-core laptops fall below this bar and will stay in fallback mode.
App control policies. SlimCore installs as MSIX packages under the user’s account. Policies such as BlockNonAdminUserInstall, AppLocker, or App Control for Business can block the install without warning. Recent Windows updates add a Group Policy setting that lets admins allow the SlimCore package names while keeping the restriction in place for other apps.
Windows thin clients. Thin clients that use Unified Write Filters need exclusions for the WindowsApps folder and the SlimCore package folder. Models that point TEMP to a RAM disk need a system variable named MSTEAMSVDI_BITS_TMP_PATH set to a physical disk location. The VDI thin client guide covers how these devices connect to hosted desktops.
Home and branch networks. Call media now flows directly from each device to Microsoft 365. Firewalls need to allow UDP ports 3478 through 3481, and the Teams endpoints Microsoft lists, and quality of service rules need to target MsTeamsVdi.exe.
Microsoft does not recommend routing Teams media traffic through a VPN, which matters for remote workers who connect from home.
Sign-in policies. With SlimCore, Microsoft Entra Conditional Access evaluates sign-ins against the device’s IP address, not the virtual machine’s. Under strict location rules, users may see repeated sign-in prompts or failed calls. Microsoft suggests relaxing strict location enforcement or adding the relevant ISP ranges to trusted locations.
Users who switch devices are covered. When a Citrix session reconnects from a different device, Teams switches between SlimCore and WebRTC without a restart. A user can work from a home Windows laptop with the plugin and an office Linux thin client in the same week.
Using Teams on a Cloud Desktop from a Mac
Mac support for the new optimization is generally available on Citrix and Azure Virtual Desktop. On Citrix, the Mac needs Workspace app 2508.10 or later with the Teams plugin. Microsoft lists macOS 14, 15, and 26 as supported, and macOS 26 requires Workspace app 2511.
Workspace app 2508.10 prompts the user to install the plugin, and Citrix Workspace app for Mac 2607 installs it automatically by default. Citrix lists 2607 or later as the recommended version for Mac. Mac users also have more time, with end of availability set for September 1, 2027.
Published Teams apps are not optimized on Mac, so those sessions fall back to server-side rendering. Mac users get optimized calls when Teams runs inside a full virtual desktop for Mac. A few features remain unavailable on Mac under the new stack, including sharing system audio.
Screen Sharing in Design Reviews
Screen sharing from a Mac works differently. When a Mac user shares a screen, Teams encodes and sends it from the virtual machine, not from the Mac. Microsoft also has this VM-side sharing in public previews for Windows devices.
In Microsoft’s load test on a 4 vCPU, 16 GB virtual machine using software encoding, sharing a 4K monitor added about 510 MB of memory and 7 to 8 percent CPU at 3 frames per second. When the user selected the option to optimize for video, CPU use rose to 25 to 30 percent at 15 frames per second. Microsoft notes that results vary by VM size and workload, and that GPU acceleration is the most important factor.
This affects BIM, CAD, and design teams on Macs who share Revit or SOLIDWORKS models in review calls. A GPU-powered virtual desktop with an allocated NVIDIA vGPU profile can encode the shared screen on GPU hardware, which frees the CPU for the 3D application. Teams calls on their own don’t need a GPU-accelerated desktop, because audio and video run on the user’s device.
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How to Check Whether Teams Is Optimized
Users can confirm their status inside Teams. The VDI status indicator at the top of the window shows whether the session is optimized, and hovering over it shows whether Teams is using SlimCore or WebRTC.
The Settings > About page also lists the mode. On Citrix, a session on the new stack reads Citrix SlimCore Media Optimized. The first time a user launches Teams, it needs two restarts before it switches to SlimCore.
If Teams shows a warning icon, the user can choose Optimize virtual desktop and restart from the three-dot menu to attempt a repair. If the session still isn’t optimized, Teams displays an error code that IT can match against Microsoft’s connection error table.
Admins can track the rollout in the Call Quality Dashboard, which labels sessions on the new stack as VDI 2.0 Optimized.
Preparing Your Team Before April 2027
Start with a list of every device your users connect to, including personal laptops, Macs, and thin clients. Compare each one against Microsoft’s minimum hardware and OS requirements.
Next, update the Citrix Workspace app on each Windows device and Mac, and confirm the Teams plugin is installed. On company-managed devices, review app control and write filter settings so the SlimCore packages can be installed.
After that, run a test call with video and screen sharing from both home connection and the office. Check the status indicator during the call and note any device that falls back.
Finally, confirm the server side with your provider, including the VDA version and the Teams version on the desktop image. On a managed desktop-as-a-service, the provider answers these questions for you, and its support team can help users who get stuck on device setup.
Move to a cloud-hosted desktop on Citrix VDA 2603 or later, with support that helps set up every device.
Frequently Asked Questions
Is migrating to SlimCore mandatory?
“After April 1, 2027, WebRTC optimization is no longer available on Windows devices connecting to Citrix, Azure Virtual Desktop, or Windows 365. Teams uses SlimCore where the device supports it. If optimization fails, calls fall back to server-side rendering on the virtual machine.
Will Teams stop working after the WebRTC deadline?
Users can still join calls and meetings, but devices that cannot run SlimCore will lose optimization. This results in lower call quality and increases load on the hosted desktop.
Are Linux thin clients affected?
Supported Linux thin clients are not affected by the deadlines. They keep the current optimization until Microsoft releases the new solution for Linux.
Can I use Teams in a web browser on a virtual desktop?
Microsoft does not support Teams for web inside VDI. Users should run the Teams desktop app within their virtual desktop.
Do users need a GPU on their own device?
No. Microsoft’s minimum requirements do not include a dedicated graphics card. The device needs hardware acceleration and DirectX 9 or later with a WDDM 2.0 driver, which most current Windows laptops already have.
