Microsoft 365 licensing is the one thing I’ve watched competent IT leaders get wrong for over a decade. Microsoft built it to be opaque, and most of the people positioned to explain it have a financial reason to keep it that way. You inherit a tenant, you run on whatever the last person set up, and one day someone in finance asks whether you’re paying for the right things. You go looking for a straight answer and there isn’t one.
I’ve been doing IT advisory work since 2012, and that gap has been sitting there the whole time. So when Mario and I were doing our yearly planning, I finally put it on the list.
Nobody gives you a straight answer
Two situations stuck with me. One was a small nonprofit client trying to make sense of their licensing and save costs, already tangled by nonprofit pricing, with no clean way to show them what they had, what they were missing, and what changing tiers would cost them. The other was my time at a global enterprise, where the team was on E3 and trying to understand what E5 would get them. We went back and forth with Microsoft directly and still came away unsure. What’s included, what isn’t, what you’re entitled to versus what you’re licensed for. It’s a maze, and it’s a maze by design.
Look at your options when you need an answer.
You can call a licensing partner. Sometimes you get a straight one. Often you get a pitch, because the partner makes more when you buy up. I’ve sat in those conversations and watched clients leave with less clarity than they walked in with.
You can read Microsoft’s documentation, which is written to sell you the next tier up.
You can Google it and inherit someone else’s outdated blog post.
You can ask AI. I leaned on it hard while building this. I used the best model available and my first two passes at the licensing data came back wrong, wrong enough to cost a client money if I’d trusted them. The knowledge cutoff is a wall for this kind of work, and the model won’t tell you when it hits it. It took a third pass and a complete rebuild of how I was prompting and indexing the data to get it accurate. No IT director should have to become a prompt engineer to find out what they’re paying for.
Every one of those options has the same flaw. None of them show you anything. You’re making a five- or six-figure decision off a conversation that left things out.
What the tool does
The Microsoft 365 Licensing Decoder puts two tiers side by side and shows you four things: cost, features, IT admin impact, and user impact.
User impact is where the surprises live. Move someone from a 100 GB mailbox down to a 50 GB mailbox, and if they’re sitting at 51 GB, they stop sending mail the moment the change takes effect. That’s a Monday-morning help desk fire, and the tool surfaces it before you make the change rather than after.
Admin impact rides along with it. Drop a tier and you can lose a portal, a management tool, or a piece of functionality you were quietly depending on to run the environment. Those are the losses nobody notices until they’re gone.
Then there’s compliance, and this is the part even experienced people get wrong.
In Microsoft 365, working and licensed are not the same thing. You can turn on an E5 feature with a single E5 license in the tenant and watch it work for everyone. Microsoft won’t stop you. But every user who benefits from that feature is supposed to be licensed for it. The software doesn’t enforce the rule. The audit does.
The same trap sits lower in the stack. The day you turn off security defaults and start writing your own Conditional Access policies, every user covered by those policies needs an Entra ID P1 license. Microsoft doesn’t warn you when you flip that switch. If you’re on Business Premium you already have P1 and you’re fine. If you’re on Business Basic, Business Standard, or a bare Office 365 plan, you may have walked yourself out of compliance without knowing it. A lot of organizations are sitting in exactly that spot right now. The tool shows you where.
Screenshot from darkstack.co
Who this is for
This is for the IT leader or admin who owns licensing and never got a clean handoff. This is for the admin or IT director who inherited a setup, has been running on it, and just got asked whether it’s right.
It’s also a defense tool, and that’s how I’d use it. The pressure almost always comes from the same direction: cut spend, find savings. You need to walk back to whoever holds the budget and either justify the current setup or show them a cleaner one. This gives you the picture, the documentation, and the numbers to win that conversation instead of guessing through it.
The savings add up because the tiers are not priced in small steps. The spread from Business Premium up to E5 is roughly two and a half times the cost per user. Put people on tiers they don’t need across a whole org and you’re often looking at 30 to 50 percent of licensing spend that right-sizing by role can recover. Most organizations have never run that math once.
One moving target to watch: Microsoft raised prices across most commercial plans on July 1, 2026, and folded Defender for Office 365 Plan 1 into E3 at the same time. That narrowed the security gap that used to send people straight to E5. If your last licensing decision predates that change, it’s worth a fresh look, and the tool reflects the current lineup.
What was hard, and what’s next
Getting the data right was the whole job. The interface was the easy part. Licensing data is fragmented, full of edge cases, and constantly moving, and Microsoft’s own documentation doesn’t capture all of it. Intune was the worst of it, where the line between Plan 1 and Plan 2 gets granular enough that you have to read it three times.
The trap that kept catching me: moving Plan 1 to Plan 2 sometimes looks like you’re losing a feature, when one capability is replacing another. On paper it reads as a downgrade. In practice it’s an upgrade. Teaching the tool to tell those apart meant rebuilding how the licensing data was indexed on the backend.
The side-by-side comparison shipped first. The features I’m excited about are next.
A plan advisor is close to done. It’s a wizard that walks through your org’s needs and tells you which tier each group of users belongs on, in as few questions as possible. The first question sorts your licensing family: commercial, nonprofit, government, or education. From there it’s yes/no, every yes moves a group up a tier, and you stop when the no’s start stacking. You come out with a recommendation per user group, not a generic suggestion.
Further out is tenant-level detection. Point it at a live Microsoft 365 environment and have it tell you where you’re out of compliance and where you’re over-licensed. That’s where this gets useful at scale.
What I want you to walk away with
Whatever you decide about your licensing, decide it with your eyes open. See the impact, understand the trade, and walk into the budget conversation able to show your work. We built this because nobody else did, and because the options that existed weren’t good enough to trust.
The beta is live. Get access at DarkStack.co and send us your feedback so we can make it sharper.
