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Windows Server licensing

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This article is about Windows Server 2025 volume and OEM/retail licensing under Per Core/CAL. For SQL Server, see SQL Server licensing. It does not replace the Windows Server white-paper galleries.

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Windows Server 2025 Standard and Datacenter are licensed under the Per Core/CAL License Model in the Microsoft Product Terms (Date Available 11/24; prior version Windows Server 2022, 8/21). Core licenses cover the server software; access requires CALs or External Connector Licenses except as the Product Terms list. Essentials is a separate OEM Server-license model, not Per Core/CAL.

Editions

Current version in Product Terms: Windows Server 2025 (Date Available 11/24). Prior Version: Windows Server 2022 (8/21). Down Editions: Datacenter to Standard or Essentials; Standard to Essentials.[1]

Edition License type Physical-core virtualization Access 
Datacenter Core licenses; Per Core/CAL Any number of OSEs on the Licensed Server Windows Server 2025 CAL (or CAL Equivalent); External Connector optional for External Users 
Standard Core licenses; Per Core/CAL Two OSEs; plus one Physical OSE if used solely to host and manage Virtual OSEs; stacking additional full Standard core-license sets for two additional OSEs each Same Base Access License / External Connector 
Essentials Server license (not Per Core/CAL). Product Terms still describe 2019 Essentials limits; retail/OEM 2025 terms: one CPU, up to 10 cores, 25 users or 50 devices, one physical + one virtual if the physical instance only hosts/manages One physical + one virtual under those limits Not the CAL model (user/device caps instead) 

Windows Server Datacenter: Azure Edition may be used only as an operating system for virtualization on Microsoft Azure and Azure Stack.[1]

Customer may use any number of Windows Server Containers without Hyper-V isolation on the Licensed Server (Standard and Datacenter). Each Hyper-V isolation instance is one Virtual OSE.[1][2]

Metrics

The catalog has ten rows for Windows Server; definitions are on the linked rows.

# Microsoft name Catalog row Unit What Microsoft says 
1 Per Core/CAL Per Core/CAL Core License Model for Standard and Datacenter. It is not SQL Server Per Core: Windows Server core licenses still require access licenses. 
2 User CAL User CAL User One user, any device. 
3 Device CAL Device CAL Device One device, any user. 
4 Base CAL Base CAL Other Windows Server 2025 CAL (and CAL Equivalent License). 
5 Additive CAL Additive CAL Other Generic Additive Access License kind. Named instances are rows 8–10. Must be used on conjunction with a base CAL (Glossary wording). 
6 External Connector External Connector Other Alternative to CALs for External Users; assigned to a Server. 
7 Server license Server license Other Windows Server Essentials OEM. Not Per Core/CAL. Up to 25 users / 50 devices; up to 10 cores and 1 VM on single-socket (educational 2025 guidance). Product Terms still describe 2019 Essentials limits. 
8 Windows Server 2025 Remote Desktop Services CAL Windows Server 2025 Remote Desktop Services CAL Other Named Additive Access License. Also required to host a GUI via RDS or other technology. Use with a Base Access License. 
9 Windows Server 2025 Active Directory Rights Management Services CAL Windows Server 2025 Active Directory Rights Management Services CAL Other Named Additive Access License. Use with a Base Access License. 
10 Microsoft Identity Manager 2016 User CAL Microsoft Identity Manager 2016 User CAL User Named Additive Access License, per user only. Also required for any person for whom the software issues or manages identity information. 

Educational (does not supersede Product Terms): Microsoft’s core-based licensing guidance distinguishes Per Core (SQL Server) from Per Core/CAL (Windows Server). Windows Server 2025 licensing guidance and Base and Additive CALs guidance explain counting in non-contractual language.

Counting / floors

Effective for the live Product Terms publication retrieved 2026-08-31 (latest listed change 10 August 2026).[6]

Physical cores (volume). License all Physical Cores on the Licensed Server, subject to a minimum of 8 Licenses per Physical Processor and 16 Licenses per Server. A Licensed Server is a single Server to which a License is assigned; a hardware partition or blade is a separate Server. Physical Core means a core in a Physical Processor; Physical Processor means a processor in a physical hardware system.[1][2] Catalog proof: Windows Server physical core floor — min 8 per processor / 16 per server (backs Windows Server physical core floor).

By Individual Virtual OSE (subscription or active Software Assurance only). The number of Licenses required equals the number of Virtual Cores in the Virtual OSE, subject to a minimum of 8 Licenses per Virtual OSE. CALs used under this model must also be subscription licenses or have active SA. Customer may reassign those Licenses to any Licensed Server in the same Server Farm as often as needed; reassignment from one Server Farm to another is not on a short-term basis (not within 90 days of the last assignment).[1] Catalog proof: Windows Server by Virtual OSE floor — min 8 licenses per Virtual OSE (backs Windows Server by Virtual OSE floor).

Educational only, does not supersede Product Terms: Windows Server 2025 licensing guidance and core-based licensing guidance also state a 16 core licenses per customer minimum when allocating licenses by virtual machine.[4][3]

OEM/retail contractual analogue (not a substitute for volume Product Terms). Microsoft Software License Terms — Windows Server, last updated July 2024: each server requires a minimum of 16 core licenses; each physical processor requires a minimum of eight core licenses. If obtained from a device manufacturer or installer, the software is licensed for 16 cores unless additional core licenses are included. Physical cores disabled for use by an operating system need not be licensed; that exemption does not reduce the 16/8 minima. Retail terms do not describe licensing by virtual machine.[7]

Access. Except as listed, all server software access requires CALs or External Connector Licenses. CALs are not required for: access by another Licensed Server; Web Workload or HPC Workload; access in a Physical OSE used solely for hosting and managing Virtual OSEs. Users do not need Windows Server CALs when accessing solely to sync Active Directory on Licensed Servers with Microsoft Entra ID. As a one-time alternative, base CALs may be dedicated to an Instance on a single Server (per server mode).[1]

Universal License Terms: assign a License before use; reassignment not less than 90 days except permanent hardware failure or loss, termination of employment or contract, or temporary reallocation.[8]

A 2025 CAL/EC may access 2025 and prior; a 2022 CAL cannot access 2025 (educational guidance table).[4]

Do not import SQL Server floors. SQL Per Core uses four Licenses per Physical Processor or per Virtual OSE, not 8/16.

Virtualization

Physical-core Datacenter: any number of OSEs on the Licensed Server. Catalog proof: Windows Server Datacenter — any number of OSEs on the Licensed Server (backs Windows Server Datacenter unlimited OSEs). Physical-core Standard: two OSEs; plus the Physical OSE if used solely to host and manage Virtual OSEs; assign another full set of Standard core licenses (same physical-core count and minima) for each additional two OSEs. Catalog proof: Windows Server Standard — two OSEs; Physical OSE host-only; stacking two more (backs Windows Server Standard OSE allotment). By-VM licensing (either edition, subscription/SA only): one Virtual OSE per licensed set, at 8 Licenses per Virtual OSE (Virtual Cores, subject to that minimum).[1]

Windows Server Container with Hyper-V isolation is one Virtual OSE. Windows Server Containers without Hyper-V isolation: any number on the Licensed Server.[1][2]

Server Farm: a single data center or two data centers each physically located either in time zones not more than four hours apart, or within the EU or EFTA.[2]

License Mobility through Software Assurance for this product: External Connector only (Windows Server OS is not a License Mobility–designated product under the general SA License Mobility rules; those apply to other designated licenses — see License Mobility through SA — shared servers, verification, 90-day, per-core 1:1). Flexible Virtualization Benefit: customers with subscription licenses or licenses with active SA (including CALs) may use licensed copies on devices, including shared Servers, under the day-to-day management and control of Authorized Outsourcers; do not expand beyond Universal License Terms / Product Terms.[1][8] Catalog proof: Flexible Virtualization Benefit — use on Authorized Outsourcers including shared Servers (backs Flexible Virtualization Benefit).

Windows Server Annual Channel for Containers: only with Datacenter core licenses with active subscription or SA, and only as an OS to host Windows Server containers with a Certified Kubernetes product.[1]

Cloud / BYOL

Product Terms for this entry point to Microsoft Azure Hybrid Benefit in the Microsoft Azure Services Product Entry for deploying Windows Server images on Microsoft Azure.[1]

Azure Hybrid Benefit — Windows Server (Cited). Eligible licenses: Windows Server Standard/Datacenter core licenses and Windows Server Standard/Datacenter processor licenses with an active subscription or Software Assurance. Each processor license is equivalent to 16 core licenses. For VM licensing, allocate enough eligible core licenses to cover all Virtual Cores on the VM(s); minimum 8 core licenses per VM. Dedicated Host licensing (Datacenter only): allocate enough Datacenter core licenses to cover all Physical Cores available on the Dedicated Host. Aside from printed migration allowances, once licenses are allocated to Azure they may not be used elsewhere; after at least 90 days, Customer may elect to stop using them for AHB.[11] Catalog proof: Azure Hybrid Benefit Windows Server — eligibility, 16/core equivalence, min 8 per VM (backs Azure Hybrid Benefit Windows Server). Product Terms publish no AHB Server+CAL→vCore conversion.

Azure Virtual Desktop for Windows Server: refer to the Azure Virtual Desktop section of the Microsoft Azure Services Product entry (not expanded here).[1]

Educational only: Microsoft licensing and pricing pages name a pay-as-you-go subscription (Azure Arc) that does not require base CALs; RDS CALs still required; unlimited virtualization is not available through PAYG on-prem Arc. That channel is not a substitute for the Per Core/CAL Product Terms.[9][10]

Programs

These Product Terms are shown for EA/EAS/SCE. Program attributes and other program suffixes (OL, MCA) exist at the same product-offering path; do not apply EA true-up math from memory.

1 April 2026 Product Terms change: Microsoft consolidated MCA Subscription Product Terms and provided rights for Subscription license customers equivalent to the rights provided to Software Assurance customers for Windows Server Standard, Datacenter, and Essentials.[6]

Related programs: Software Assurance; Azure Hybrid Benefit (AHB WS proof Azure Hybrid Benefit Windows Server — eligibility, 16/core equivalence, min 8 per VM); Flexible Virtualization Benefit (FVB proof Flexible Virtualization Benefit — use on Authorized Outsourcers including shared Servers); License Mobility through Software Assurance (for this product: External Connector only — see Virtualization).

Software Assurance table (this product): Disaster Recovery all editions; License Mobility External Connector only; Self Hosting all except Essentials. For Subscription licenses, during the term, Customer is additionally granted rights equivalent to SA customers (this product’s SA Equivalent Rights cell is None in the EA table; MCA consolidation is the 1 April 2026 change above).[1]

SPLA is named as a channel on educational pages; no Services Provider Use Rights document was retrieved, so SPLA metrics are not covered here.

Out of scope

  • SQL Server — separate License Models (Per Core and Server/CAL). Do not apply the Windows Server 16-core server floor to SQL Server.
  • Azure Hybrid Benefit SQL ratios / Server+CAL→vCore — SQL AHB ratios and any Server+CAL→vCore conversion are out of scope here (AHB Windows Server eligibility / 16-core processor equivalence / min 8 per VM is Cited above).
  • SPLA / SPUR, RDS hoster math, and EA enrollment true-up formulas not stated in the documents cited below.
  • Introduction to Microsoft Core Licensing PDF (April 2017) — stale (Core Factor / Windows Server 2016 era). Prefer live Product Terms and the 2025 core-based licensing guidance web page.
  • Existing Windows Server white papers in this wiki are archives; this page sits alongside them and is not a replacement.

Catalog rows

Sample catalog rows for this article, grouped by table.

References

  1. Microsoft Product Terms — Windows Server Standard, Datacenter, and Essentials (EA/EAS/SCE)Live publication; latest listed Product Terms change 10 August 2026; WS 2025 Date Available 11/24Retrieved 2026-08-31.
  2. Microsoft Product Terms — GlossaryLive publication; latest listed Product Terms change 10 August 2026Retrieved 2026-08-31.
  3. Core-based licensing models (licensing guidance)Educational; does not supersede Product TermsRetrieved 2026-08-31.
  4. Windows Server 2025 licensing guidanceEducational; does not supersede Product TermsRetrieved 2026-08-31.
  5. Base and Additive CALs licensing guidanceEducational; does not supersede Product TermsRetrieved 2026-08-31.
  6. Microsoft Product Terms — Summary of ChangesLatest listed change 10 August 2026; MCA SA-equivalent rights 1 April 2026Retrieved 2026-08-31.
  7. Microsoft Software License Terms — Windows Server (retail/OEM, Datacenter and Standard)Last updated July 2024 (OEM/retail contractual; volume agreement takes the place of this if applicable)Retrieved 2026-08-31.
  8. Universal License Terms for all Software (EA/EAS)Live publication; assignment/reassignment and multiplexingRetrieved 2026-08-31.
  9. Microsoft Windows Server licensing resourcesEducational / FAQ (PAYG CAL exception)Retrieved 2026-08-31.
  10. Windows Server 2025 Licensing and PricingEducational / list price (16 core licenses; PAYG)Retrieved 2026-08-31.
  11. Microsoft Product Terms — Microsoft Azure (Azure Hybrid Benefit)Live publication; AHB Windows Server eligibility / allocationRetrieved 2026-08-31.
  12. Product Terms — Windows Server Standard, Datacenter, and Essentials (EA/EAS)Catalog: Product Terms — Windows Server Standard, Datacenter, and Essentials (EA/EAS)Effective 2026-08-10. Retrieved 2026-08-31.
  13. Product Terms — Microsoft Azure (Azure Hybrid Benefit)Catalog: Product Terms — Microsoft Azure (Azure Hybrid Benefit)Effective 2026-08-10. Retrieved 2026-08-31.
  14. Product Terms — Software Assurance Benefits (License Mobility)Catalog: Product Terms — Software Assurance Benefits (License Mobility)Effective 2026-08-10. Retrieved 2026-08-31.
  15. Product Terms — For all Software (Flexible Virtualization Benefit)Catalog: Product Terms — For all Software (Flexible Virtualization Benefit)Effective 2026-08-10. Retrieved 2026-09-15.
  16. Core-based licensing models overviewCatalog: Core-based licensing models overviewEffective 2026-08-31. Retrieved 2026-09-15.

See also

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