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You have a Windows Server sitting in the corner (or in a data center), and you want your team to log into it remotely with Remote Desktop. You fire up more than a couple of sessions, and suddenly the server starts refusing connections after 120 days. Welcome to the world of RDS CALs — the licenses almost nobody warns you about until Remote Desktop Services stops letting people in.
The confusing part isn’t buying them. It’s figuring out how many you need and whether to choose Per-User or Per-Device mode. Get it wrong and you either overspend or lock yourself into the wrong licensing model. This guide explains the whole thing in plain English, walks through real staffing examples, and shows you where to get genuine CAL packs without paying enterprise prices.
- Every user or device connecting via RDS needs its own RDS CAL — this is separate from the Windows Server license and standard Windows Server CALs.
- You choose one mode per RD licensing server: Per-User or Per-Device. It is not concurrent (floating) licensing.
- Per-Device is cheapest when many people share fewer machines (shift work, kiosks). Per-User wins when people roam across laptops, phones, and home PCs.
- RDS CALs are version-specific: a 2019 CAL covers Server 2019 and older, but not Server 2022 or 2025. Buy for your server version.
- Windows Server gives you 2 free administrative RDS sessions — anything beyond that needs proper CALs.
What an RDS CAL actually is
A CAL is a Client Access License — permission for a client to use a server service. Windows Server itself needs two kinds of licensing to run Remote Desktop properly, and this trips up a lot of first-timers.
First, there’s the base Windows Server license plus standard Windows Server CALs, which cover the basic right to use the server (files, authentication, printing, and so on). That’s the foundation. But the moment you want people to actually log in with a full remote desktop session, you enter Remote Desktop Services territory, and RDS CALs are a completely separate layer stacked on top.
So the math is: Windows Server license + Windows Server CALs + RDS CALs. The RDS CAL is the piece that specifically unlocks remote desktop sessions beyond the built-in administrative allowance. Think of the Server CAL as the ticket into the building and the RDS CAL as the ticket to sit at a remote workstation inside it.
Once you install the RD Licensing role and activate your CALs, the licensing server hands one out to each connecting user or device automatically. You don’t assign them by hand day-to-day — you just need to own enough of them to cover everyone who connects.
Per-User vs Per-Device
Here’s the decision that causes the most head-scratching. When you set up your RD licensing server, you commit to one mode. It is not concurrent licensing — you can’t buy 10 CALs and rotate them among 30 people based on who’s online. Instead:
- Per-Device: a CAL is tied to each physical device that connects. Ten shared PCs = ten CALs, no matter how many people use them.
- Per-User: a CAL is tied to each named user account. Thirty employees = thirty CALs, no matter how many devices each person uses.
The right choice comes down to the ratio of people to devices. Use this table to see which mode is cheaper for common setups:
| Scenario | People vs Devices | Cheaper mode | Why |
|---|---|---|---|
| Shift workers sharing a pool of PCs | Many users, few devices | Per-Device | Three shifts share one machine but only need one device CAL |
| Call center with fixed desks | Users ≈ devices | Either | Roughly 1:1, so pick based on future growth |
| Remote/hybrid staff on laptops + phones + home PCs | Few users, many devices | Per-User | One person, many devices = one user CAL covers all of them |
| Kiosks or point-of-sale terminals | Anonymous users, fixed devices | Per-Device | No named accounts; the device is the constant |
The quick rule: count whichever number is smaller. If you have fewer devices than people, go Per-Device. If you have fewer people than devices, go Per-User. That’s the whole trick.
Worked examples: how many do I need?
Abstract rules are easy to nod along to and hard to apply. Let’s run the numbers on three realistic small businesses.
Example 1: Warehouse with 20 employees and 10 shared PCs
Twenty staff work across two shifts, and they share 10 terminals on the floor. Nobody has a personal machine. Since the devices are the smaller, fixed number, Per-Device is the clear winner: you buy 10 Device CALs, not 20. The 20 people cycle through those 10 licensed machines all day and everyone stays covered.
Example 2: Accounting firm with 8 staff who work from anywhere
Eight accountants each connect from an office desktop, a laptop at home, and sometimes a tablet. That’s potentially 24 devices for 8 people. Here Per-User is obvious: buy 8 User CALs, one per person, and each accountant can log in from as many devices as they like without adding a single license.
Example 3: Growing startup, 35 employees, one laptop each
Thirty-five people, thirty-five laptops — a near 1:1 ratio. Either mode costs the same 35 CALs today. Because the team is hiring and people will inevitably add a phone or a second device, Per-User is the smarter bet for headroom. And since CALs come in packs, a single 50-CAL pack covers all 35 with room to grow to 50 before you need to buy again.
Matching the CAL to your server version
RDS CALs are version-specific, and this is where people accidentally waste money. The rule is simple: a CAL must match or exceed your server’s version. A CAL is backward compatible, not forward compatible.
- A Server 2019 RDS CAL works on Server 2019, 2016, 2012 R2, and earlier — but not on Server 2022 or 2025.
- A Server 2022 RDS CAL works on 2022 and everything older, but not on 2025.
- A Server 2025 RDS CAL covers 2025 and everything below it.
So the safe move is to buy CALs that match the newest server they’ll ever touch. If you run a Server 2022 host, buy 2022 CALs. If you’re deploying fresh on Server 2025, buy 2025 CALs. Don’t buy older, cheaper CALs hoping they’ll cover a newer server — they won’t activate, and your users will get locked out.
Where to buy cheap RDS CALs
RDS CALs from big-box resellers are notoriously overpriced, often running into hundreds of dollars per small pack. SoftKeys sells genuine 50-CAL packs at a fraction of that, in both Device and User flavors, for every major server version. One 50-pack covers most small and mid-size businesses in a single purchase — and because they’re real Microsoft licenses, they activate through your RD Licensing server exactly as they should.
📦 Genuine RDS CAL Packs (50 CALs)
Frequently Asked Questions
Yes. Standard Windows Server CALs cover basic access to the server, but Remote Desktop sessions require a separate RDS CAL for each connecting user or device. You need both layers: the base server license and its CALs, plus RDS CALs.
No. RDS CALs are not concurrent or floating. In Per-User mode each named user needs a CAL; in Per-Device mode each device needs one. You cannot legally share a small pool of CALs across a larger group based on who’s online at a given moment.
Only for administration. Windows Server allows up to 2 administrative Remote Desktop sessions without RDS CALs. Any additional sessions, or any regular (non-admin) user access, requires proper RDS CALs once the built-in grace period ends.
Compare your number of users to your number of devices, and license the smaller one. Many people sharing few machines? Go Per-Device. Few people using many machines? Go Per-User. You commit to one mode per RD licensing server.
No. CALs are backward compatible only. A 2019 CAL runs on Server 2019 and earlier but not on Server 2022 or 2025. Always buy CALs that match or exceed your newest server version.
Once your available CALs are all assigned, new users or devices are refused a Remote Desktop session, or fall back to a temporary grace period that eventually expires. The fix is simply to buy more CALs matching your server version and add them to the licensing server.
Final thoughts
RDS licensing sounds intimidating, but it comes down to two questions: how many users or devices connect, and which of those two numbers is smaller. Count the smaller one, pick that mode, match the CAL to your server version, and buy a pack that leaves a little room to grow. A single genuine 50-CAL pack covers the vast majority of small businesses for years — without the enterprise-reseller markup. Get the mode right up front and you’ll never think about RDS licensing again.
