Do I have to repurchase Windows when upgrading my SSD?

Whether you'll need to buy Windows again depends. If you installed Windows yourself, you’re probably fine. Check the Microsoft link for reactivating Windows after hardware changes just to be safe.

If you have a bootable USB for Windows, create one using the media creation tool. Make sure to note your product key using the command prompt; you can enter it during installation on the new SSD. Alternatively, if both SSDs are installed, you can run Windows from the smaller one while getting everything set up on the new one.

You shouldn't have to buy Windows again, unless you're using it on a different machine. Sometimes a hardware change can trigger activation issues since the license is tied to your original hardware setup. If you've associated your license with a Microsoft account, it should be smooth. If there are problems, Microsoft support can help you transfer the license from your old setup to the new one.

I had to buy a new code for Windows when I upgraded my SSD. It wasn't too expensive, just around 6 bucks from a key site. You might find a workaround, but in my case, when I reinstalled, it didn’t recognize my hardware and needed reactivation.

Just clone your existing drive to the new SSD! There are free SSD cloning tools out there, and this way you won't need to mess with Windows reinstalling. Check online for guides on how to do it. It’s really straightforward.