Microsoft cloud
Session host
Azure Virtual Desktop session host
An Azure Virtual Desktop session host is a virtual machine, running in an organisation's own Azure subscription, that has the Azure Virtual Desktop agent installed and is registered into a host pool, making it available to run remote desktop or published application sessions for end users.
Why Session host matters in a Microsoft estate
Session host matters because Microsoft 365, Azure, Windows 365, Teams, and related services are usually managed as one estate. The term connects to planning, cost, configuration, security, and day-two operational decisions across that estate.
How Session host shows up in practice
It is the actual compute resource being consumed, in contrast to Windows 365, where the underlying compute is abstracted away from the organisation entirely inside a fixed-fee Cloud PC. Session hosts come in two operating system modes with materially different economics and use cases. Single-session hosts have one Windows machine serving exactly one concurrently connected user, similar in shape to a traditional VDI desktop. Multi-session hosts use the Windows 11 (or 10) Enterprise multi-session edition that only Azure Virtual Desktop is licensed to run, where many users share sessions on the same underlying virtual machine simultaneously.
This is the configuration that gives Azure Virtual Desktop its cost advantage over both traditional VDI and Windows 365 at scale, since compute cost is shared across many concurrent sessions rather than dedicated one-to-one per user. Session hosts are organised into host pools, which group hosts with an identical configuration and image together and apply a load-balancing algorithm. This is either breadth-first, spreading new sessions evenly across all available hosts to maximise per-user performance, or depth-first, filling one host to its configured maximum session limit before moving to the next.
Depth-first is typically chosen to allow autoscaling to deallocate and stop unused hosts entirely, and stop paying for their compute, during low-usage periods. That autoscaling behaviour is where Azure Virtual Desktop's cost model diverges most sharply from Windows 365's fixed monthly fee. Because session hosts are ordinary Azure virtual machines billed by the hour, organisations that configure scaling plans correctly, powering hosts down outside business hours and scaling host count to match actual concurrent demand through the day, can achieve substantially lower effective per-user cost than a fixed-fee Cloud PC model.
This only holds if the scaling plan is actually tuned to real usage patterns; a host pool left running at a fixed size around the clock loses that advantage entirely and can end up more expensive than the Windows 365 equivalent for the same user population. Session host maintenance is an ongoing administrative responsibility that Windows 365 largely abstracts away from the organisation. Patching, image updates, agent updates, and monitoring host health for issues like FSLogix profile container failures or capacity exhaustion all fall to whoever administers the host pool. This is the direct trade-off for the deeper cost and configuration control Azure Virtual Desktop offers over the simpler, more managed Windows 365 model.