What is a CAL?
Last reviewed by the MSLicenseHub Licensing Desk.
A Client Access License (CAL) authorizes a user or device to access a Microsoft server product such as Windows Server, Exchange or SharePoint. The server itself needs its own server license; the CALs cover who connects to it. Without enough CALs, you are technically out of compliance even if every server license is paid for.
CALs come in two flavors. A User CAL follows a person across every device they use, which is the right choice for staff with a laptop, a phone, and a desktop. A Device CAL is tied to a specific machine and covers anyone who logs into it — better for shift workers who share kiosks or shop-floor PCs.
Apply this to your deployment
- Server licence
- User or device
- CAL version
Check the server licence separately from access rights. Concurrent connections do not replace the count of licensed users or devices; verify exceptions and CAL versions against the specific product terms.
Decision checklist
| Check | What to record |
|---|---|
| Product and version | Record the full name, edition, version and part number in the quote. |
| Scope of use | Identify the user, device or deployment; count only the metric applicable to this product. |
| Evidence and support | Retain the agreement, invoice and support lifecycle date; perpetual licensing does not mean perpetual support. |
Official Microsoft terms and licensing guidance · Product support lifecycle
Practical checklist
- A Client Access License (CAL) gives a user or device the right to access server software such as Windows Server, Exchange or SharePoint.
- CALs are separate from the server licence itself.
- You choose User CALs or Device CALs according to how people use devices.
- The CAL version must match or be newer than the server version it accesses.
Common mistakes to avoid
- Thinking a server licence includes user access.
- Counting simultaneous connections instead of users or devices.
- Buying RDS CALs but forgetting Windows Server CALs.
Official source: Microsoft documentation. Licensing terms change; confirm against the current Product Terms before buying.
Still unsure?
Talk to a licensing specialist for a written, signed quote tailored to your environment.
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