What are CALs (Client Access Licences)?
Client Access Licences (CALs), also known as access licences or client access licences, are usage rights that allow a user or a device to access a Microsoft server. Whilst the server software itself may be installed and operated, CALs govern who or what is permitted to access that server.
CALs are a key licensing element, particularly in Microsoft infrastructures within the corporate environment – for example, with Windows Server, Exchange Server or certain versions of SQL Server.
Difference between a server licence and an access licence
A server licence authorises the installation and execution of the server software on a specific piece of hardware or virtual machine.
A CAL (Client Access Licence), on the other hand, authorises users or devices to access these server services – for example:
- Logging on to an Active Directory domain
- Using file and print services
- Accessing mailboxes in Exchange
- Connecting to Remote Desktop sessions
Important: A server licence alone is not sufficient in many scenarios. Without the appropriate access licences, access is not covered by the licence terms.
Which products require CALs?
CALs are required for, amongst other things:
- Windows Server
- Microsoft Exchange Server
- Microsoft SQL Server (in the Server+CAL model)
- Remote Desktop Services (RDS)
Not every Microsoft product uses the CAL model – some server versions are licensed exclusively on a core-based basis. Careful licence planning is therefore essential.
What types of CALs are there?
Depending on the server product and usage scenario, there are different types of access licences.
User CAL – access per user
A User CAL is assigned to a specific individual. This person may access the server from any number of devices.
Typically for:
- Employees with a desktop, laptop and smartphone
- Flexible working arrangements
- Working from home & mobile working
Device CAL – access per device
A Device CAL is assigned to a specific end device. Multiple users may use this device to access the server.
Typical for:
- Shift work
- Production environments
- Call centres or kiosk systems
RDS CAL (Remote Desktop Services)
An RDS CAL is also required if users access a Windows Server via Remote Desktop. It supplements the standard Windows Server CAL. Without an RDS CAL, permanent productive remote access is not correctly licensed.
Exchange Server CAL
For Microsoft Exchange Server, one Exchange CAL is required per user or device. The following are also available:
- Standard CAL
- Enterprise CAL (an add-on to the Standard CAL with extended functions such as archiving or compliance features)
SQL Server CAL
In the SQL Server ‘Server + CAL’ model, an SQL CAL is required for every user or device accessing the server, in addition to the server licence.
Alternatively, there is a purely core-based licensing model without CALs.
Windows Server CAL
The Windows Server CAL entitles users or devices to access basic server services such as:
- Active Directory,
- file and print services,
- Group Policy,
- DNS/DHCP.
User CAL vs. Device CAL – Which licence is best?
The choice between a User CAL and a Device CAL depends heavily on the organisation’s structure.
Scenarios for organisations with fixed workstations
In environments with fixed workstations and multiple staff members per device (e.g. production or shift systems), a Device CAL is often more cost-effective.
One device = one licence, regardless of the number of users.
Scenarios with multiple devices per user
If an employee works with multiple devices (PC, laptop, tablet), a User CAL is usually cheaper and more flexible.
One user = one licence, regardless of the number of devices.
Typical real-world examples
- 10 employees, 10 PCs → Device or User CAL are comparable in terms of cost
- 10 employees, 3 devices each → User CAL clearly advantageous
- 3 shifts, 10 PCs → Device CAL is significantly more efficient
A careful analysis saves on licence costs in the long term.
RDS CAL – Licensing Remote Desktop correctly
Remote Desktop Services require additional licensing.
Difference between a Standard CAL and an RDS CAL
A standard Windows Server CAL allows access to server services. An RDS licence is also required if users wish to establish a graphical remote desktop session. Both licences are necessary.
When are additional RDS access licences required?
As soon as more than the standard administrative connections are used (production environment), RDS CALs are mandatory.
Typical scenarios:
- Terminal servers
- Remote workstations
- Centralised application delivery
Licensing per user or per device for RDS
RDS CALs are also available as:
- User RDS CAL
- Device RDS CAL
and are subject to the same cost-effectiveness considerations as standard CALs.
Combining client access licences correctly – Common licensing models
Server + CAL model
A server is licensed, with each user or device accessing it requiring a CAL. This licensing model is particularly suitable for medium-sized businesses with a clear user structure.
Core-based licensing vs. CAL model
With core-based licensing, licensing is per processor core, meaning no additional CALs are required – as is the case, for example, with SQL in the core model. The CAL model, on the other hand, is characterised by lower initial costs and is cost-effective when the number of users remains manageable.
Mixed environments & hybrid scenarios
Many organisations use combined models:
- Core licensing for SQL
- Windows Server + CAL
- RDS add-on licences
A structured licensing strategy prevents over- or under-licensing.
How much does a CAL cost?
The cost of a Client Access Licence depends on several factors.
Pricing factors (product, version, licence type)
- Server product (Windows, Exchange, SQL)
- Version (e.g. 2019, 2022, 2025)
- User or Device
- Standard or specialised CAL (e.g. RDS)
Differences between standard and specialised CALs
Standard CALs are cheaper. Specialised CALs such as RDS or Enterprise add-ons are generally more expensive, as they unlock additional features.
Cost-effective licence planning for businesses
A thorough needs analysis saves costs in the long term. The choice between user and device licences, as well as between the core and CAL models, has a significant impact on the budget.
Our licensing experts will be happy to assist you with a personalised consultation: we analyse your existing server environment, review user structures and show you the most cost-effective licensing strategy – transparent, secure and tailored to your needs.
Your benefits when purchasing CALs and access licences from LizenzDeals24
At LizenzDeals24, you’ll receive your CALs and access licences quickly and easily via digital delivery by email. You’ll receive an original product key as well as legally compliant licences that are transparently documented. Thanks to attractive prices, businesses and IT service providers in particular benefit from cost-effective terms when purchasing in bulk.
Furthermore, we not only assist you with installation and activation, but also advise you on choosing the right CAL and access model – for example, when deciding between user-based and device-based CALs, or between Server+CAL and Core licensing. This ensures that your server environment is licensed cost-effectively, correctly and in a future-proof manner.
