Why am I being charged for Google Gemini API?

I’m confused as to why is Google charging me for their gemini API usage even tho it says on their website that some of their API are free to use. The whole wording is confusing. I’m reading through this documentation and it states that gemini-3-flash-preview is free to use see here.

In the real word usage, it’s NOT free to use. Why? Got no idea and would like understanding. Thanks!

BUMP? Please need to understand.

Hello, can anybody explain? The documentation isn’t clear.

just write to support. I doubt Google employees here will give you an exact reason why. They will also direct you to support because only they can see what’s going on with your account.

Btw, when you generate an API key, there was “free tier” thing. if your project has billing activated, then APIs in that project are not free tier APIs. At least this is how it was few weeks ago.

make sure your project doesn’t have a billing account associated so it’s considered as free usage.

btw you will exhaust your limits with a few queries this way, even though those models are free to use. (in my experience 15-20 calls to gemini 2.5 flash exhausted daily limit on free tier)