Is Khan Academy 100% free?

Hello there, I've heard a lot about Khan Academy and their educational resources. It's great to see that they're making learning accessible to so many people. But I'm curious, is Khan Academy truly 100% free, or are there any hidden costs or fees that I should be aware of? I'd like to make sure I'm not missing anything before I dive in and start using their platform. Thanks in advance for any insights you can provide!