In short: A Microsoft CAL (Client Access License) is not software. It is the right to access the services of a Windows server. It is assigned per person (User CAL) or per device (Device CAL) and applies on top of the server license. If you use Remote Desktop, you also need RDS CALs. The CAL version must be as new as the server.
Key Takeaways
The server and the CALs are licensed separately. Without matching CALs, access is not licensed
User CAL: one person, access to numerous devices
Device CAL: one device, access to numerous people
The CAL version must be the same as or newer than the server
Remote Desktop needs additional RDS CALs. The grace period is 120 days
With many external users, an External Connector can be cheaper
What Are Client Access Licenses (CALs)?
A CAL entitles a user or a device to use the services of a Microsoft server, such as file sharing, print services, or Active Directory. The server itself is licensed separately, per processor core in the case of Windows Server. A CAL is a usage right, not an installation medium and not a key for the server. If you count CALs incorrectly, you risk back payments in an audit. Microsoft publishes the official rules on its licensing site.
A CAL covers the Windows Server services in your environment, not just a single server. You don’t need new CALs for every additional server as long as the version fits. For more detailed information, see our article on Windows Server 2022.
User CAL or Device CAL?
Criterion | User CAL | Device CAL |
Licenses | One Person | One Device |
Access | From Any Number Of Devices | By Any Number Of People |
Fits | Staff With Laptop, Phone And Tablet, Home Office, BYOD | Shift Work, Call Centres, Shared Workstations |
Determines the count | Number Of People | Number Of Devices |
You may combine both types, for example User CALs for the office and Device CALs for terminals in production. What matters is that every access is covered by one of the two.
A three-question decision aid:
Do employees use several devices? That points to User CALs.
Do several people share one device? That points to Device CALs.
Both? Count each group separately and choose the cheaper option.
How to Count Correctly: An Example
A mid-sized company has 25 office workers who each use a laptop and a smartphone, and 10 warehouse terminals shared by 30 shift workers.
25 office workers: 25 User CALs, because each person uses several devices.
10 terminals: 10 Device CALs, because several people share one device.
Total: 35 CALs instead of 55 (25 plus 30 people).
Plan for growth: New staff, more access from home, and new applications raise the number quickly. For more on remote scenarios, read our post on home office for IT teams.
The Version Rule: Which CAL for Which Server?
The CAL must be at least as new as the server being accessed.
Case | Allowed? |
Server 2025 CAL, access to Server 2025 | Yes |
Server 2025 CAL, access to an older server version | Yes |
Older CAL (for example 2019), access to Server 2025 | No |
When you change servers, the newest CAL version is usually the safest choice. The older servers are also covered under the newest CAL.
RDS CALs: Access via Remote Desktop
According to Microsoft Learn, every user and device that connects to a Remote Desktop Session Host running Windows Server needs an RDS CAL, in addition to the normal CAL.
Particulars | RDS per device | RDS per user |
Assigned to | The device | The user in Active Directory |
Temporary CAL | Yes, 90 days from first sign-in | No |
Tracking | Also without Active Directory | Not in a workgroup |
Revoking | Up to 20% of CALs | Not possible |
Over-allocation | Not possible | Possible, but breaches the license terms |
RDS CALs follow a stricter version rule: A session host running Windows Server 2025 accepts only 2025 CALs, while a 2022 host accepts 2022 and 2025 CALs. An older RDS CAL can’t access a newer server.
Grace period: There is a 120-day period in which no license server is needed. After that, every client needs a valid RDS CAL before it can start a session. For the per-user variant, Windows doesn’t enforce licensing technically, so the administrator is responsible.
External Connector: When Outsiders Access the Server
For external users such as customers, suppliers, or partners, you can license an External Connector per server instead of many CALs. Employees and employees of affiliated companies don’t count as external. The connector doesn’t cover Remote Desktop, which has its own RDS CALs or an RDS External Connector.
Worked examples from advisory sources put the break-even at just under 50 external users per server. That depends on prices, shifts with several servers, and is not a Microsoft figure.
Special Case: Windows Server Essentials
The Essentials edition is meant for small environments. It is limited to 25 users and 50 devices and one CPU with up to 10 cores, and it needs no CALs within those limits. If you outgrow it, you move to Standard and buy CALs.
What Do Microsoft CALs Cost?
There is no single price. It depends on version, license channel, and reseller. A current German reseller pricing example (excluding VAT, Windows Server 2025) includes:
Product | License type | Net price |
Device CAL, 1 unit | OEM/ROK | €49.00 |
User CAL, 1 unit | OEM/ROK | €59.00 |
Device CAL | CSP perpetual | €42.04 |
User CAL | CSP perpetual | €54.04 |
For example, with 25 User CALs and 10 Device CALs, the OEM single prices give 25 × €59 + 10 × €49, so €1,965 net. OEM licenses have restricted rights, so ask the reseller about the terms. RDS CALs cost extra; the prices fluctuate, so check them before you buy.
Common Licensing Mistakes
Counting only servers: The server license doesn’t replace CALs.
Outdated CAL version: After a server upgrade, an older CAL no longer covers the new server.
Forgetting outsiders: Customers, suppliers, and partners don’t count as employees.
Overlooking RDS: Remote access needs additional RDS CALs, including from home.
No documentation: Without proof, nothing can be demonstrated in an audit.
Best Practices for CAL Licensing
Take stock: Who accesses which server with which device? Are there shifts, home office, or external users?
Document: Record licenses, versions, and proof of purchase. Hidden systems are a common gap, to know more about these gaps, you can read our article on shadow IT shows.
Plan for growth: New staff, more remote access, and new servers raise demand.
Choose the current version: A newer CAL also covers older servers.
Review regularly: Compare numbers and access once a year.
For help with strategy, see our articles on IT support trends and why businesses in Germany choose TechNow for IT support.
Conclusion
CALs are the ticket to the server. Whoever runs the server must license the access. A clear licensing strategy protects against back claims and makes costs predictable. If you’re unsure, have your environment reviewed, which often costs less than relicensing after an audit.
TechNow reviews your server environment and the right licensing strategy. Learn more about our IT consulting, IT support, and IT services. Looking for a provider? Read the top 10 IT support companies in Germany.
FAQ
What is a Microsoft CAL?
A Client Access License gives a user or device the right to access the services of a Microsoft server, such as file sharing, print services, or Active Directory. It isn’t software you install.
What is the difference between a User CAL and a Device CAL?
A User CAL licenses one person with any number of devices; a Device CAL licenses one device with any number of people. User CALs fit staff with several devices; Device CALs fit shift work and shared workstations.
Do I need a separate CAL for every server?
No. A User or Device CAL covers several Windows servers in your environment, provided the CAL version matches or exceeds the server version. The servers themselves are licensed separately.
How many CALs do I need?
Count users and devices separately and choose the cheaper option. If 90 employees share 30 workstations, 30 Device CALs are cheaper than 90 User CALs.
Do I need an extra license for Remote Desktop?
Yes. Every user and device that connects to a Remote Desktop Session Host needs an RDS CAL in addition to the normal CAL. After the 120-day grace period, it must come from a license server.
How much does a Microsoft CAL cost?
It depends on version, license channel, and reseller. One reseller example for Windows Server 2025: €49.00 (Device CAL) and €59.00 (User CAL), both OEM and net. Check current prices.
Can I download Microsoft CALs?
No. A CAL is a license, not software. You acquire the usage right and document it. RDS CALs are additionally installed on a license server.
Do I need CALs for Windows Server Essentials?
Not within the limits of 25 users and 50 devices. Beyond that, you move to Standard and buy CALs.