Tool for creating license keys

Hello!
What tools for creating license keys do you use?
Or write by yourself?
I want the key looks solid)
Free preferably

What do you want this for?

you either can't get it free because you'll need a DRM server with monthly payments for the server, or it won't be secure because if you use a simple internal check it can easily be hacked.

Like he said, you'll need a DRM server, and that isn't free. Hacking isn't something you should worry about, unless you plan to sell 100k+ copies, and even then I'm not sure it would be much beneficial. If people really want to hack it, they will find always find a way. The more you invest in security, the longer they will take to crack it. Most of the money a game makes come in the first year of its release, so even AAA companies don't pay indefinitely for a DRM server for their games.

To worry about piracy, you must first have a product that will be a certain hit. So, I wonder why asking such a question? Can you please explain it? We might probably be able to help you out on that, but as it is, it is too broad as a topic.

By the way, AAA companies do their best to create anti piracy methods, and games, in the end, get cracked. So here comes the second question. Do you believe you can fight this with a free solution?

What a developer should be thinking, is not creating a good anti piracy countermeasure, but a good game. If you got a good game, you will succeed. If you got a crappy game with great DRM, it's obvious that nobody will buy it. Which scenario is better?

Oh! I do not expect that someone will immediately start hacking my game. But in the future I would like to monetize it and sell licenses for a low price.

Your aspiration is right. You want to get a service to take care of licensing for you. You can google .net software licensing and you will see there are plenty of options out there. There is a big range in cost so look around. There are many solutions for any amount.

Thanks for the advice. I did just that) And I got a huge list of programs, but I don’t know what to choose. I'm a little confused

This is normal at the beginning of the journey. You may be a little puzzled. But you will understand.
I heard good reviews about programs like ArmDot. This program is commercial. Perhaps it's better to use something free for start.
Do not forget to improve your program. It must be high quality so user wants to get the key from it.

Thank you for your understanding, it is very important to me.
I will work on my program.
Good luck to all)