Nice classes, explained without a lawyer
It is the idea that explains almost everything that looks contradictory about trade marks, starting with why your name can be taken and available at once.
A trade mark does not protect a word. It protects a word for certain goods and services. That single sentence explains why a search that says "this name is registered" is almost never the end of the story, and why one that says "this name is free" is almost never proof of anything.
Forty-five drawers
The Nice Classification, an international agreement administered by WIPO and used by essentially every trade mark office in the world, sorts all commercial activity into forty-five classes: classes 1 to 34 for goods, 35 to 45 for services. When you file, you say which classes you want. You pay per class. And you are protected in the classes you paid for, not in the others.
So an identical name can belong to a furniture maker in class 20 and to a consultancy in class 35 without either of them being able to do anything about the other. They do not compete, the public does not confuse them, and the law sees no problem.
Where it stops being simple
Two limits are worth knowing before you relax.
The first is similarity. Protection does not end neatly at the edge of the class. An office or a court weighs how alike the signs are and how alike the goods or services are, together: very similar services can make a modest resemblance fatal, and very distant services can make an identical name harmless. Class boundaries are an administrative convenience, not a wall.
The second is reputation. A mark with genuine renown is protected well beyond its own classes, because trading on its fame is the harm the law is guarding against. You are not going to open a consultancy called after a famous soft drink and argue that beverages are class 32.
Choosing yours
The temptation is to file in many classes for safety. It is a bad trade. Each class costs money at filing and at every renewal, and a mark registered for goods you never sell can be revoked for non-use after five years — so the extra classes give you a bill now and nothing later.
The workable rule: file for what you actually sell today, plus what you can honestly say you will be selling within five years. For most digital businesses that is class 42 (software and technology services), class 35 (business services, advertising, retail) and, if you publish or teach, class 41.
What this changes about checking
It changes the question. Not "is this name taken?" — which has no useful answer — but "is this name taken in the classes where I am going to trade, and is there anything close enough in neighbouring classes to be a problem?" That is a longer question, and it is the one worth paying to have answered.