Once an office crosses roughly 15-20 computers, "everyone logs in with their own local Windows account" starts breaking down quietly. Passwords live in people's heads, an ex-employee's laptop still has access to shared folders, and nobody can say for certain who can open the finance drive. This is the point where an Active Directory (AD) server earns its cost.
What AD actually does
An AD server is a central login and permissions system. Every laptop and desktop "joins the domain" instead of running as an island. From that point:
- One username and password works across every machine in the office
- IT can create, disable, or delete a user account from one place — no chasing individual PCs when someone leaves
- Access to shared drives, printers, and folders is controlled centrally, not machine by machine
- Password policy (minimum length, expiry, lockout after failed attempts) applies everywhere at once
What it looks like in practice
On a recent domain migration project, I moved two offices — Bangalore and Mumbai — from a plain Workgroup setup to a proper AD domain. Before that, each machine was configured separately: local accounts, local folder permissions, no consistent password rules. After the migration, HR could report a resignation in the morning and the account was disabled by afternoon, no physical access to the laptop required.
At another client, an 80-person office, I deployed AD alongside Group Policy (GPO) rules — the two are usually set up together, since GPO is how AD actually enforces restrictions rather than just handling logins.
Signs your office is ready for it
- More than ~15 systems, or growing fast
- Shared folders where "who can see what" is unclear or based on trust rather than settings
- Repeated password reset requests because everyone forgets a different password for a different machine
- New hires take more than a day to get properly set up
- No clean way to revoke access when someone leaves
What it costs, roughly
You need one server (physical or virtual — a modest machine or a cloud VM works for most small offices) running Windows Server, plus setup time. For an office of 20-80 users, this is typically a few days of configuration work, not weeks. The ongoing cost is minor compared to the time lost to account chaos, forgotten passwords, and access nobody can explain.