Which Google API is free?

Excuse me, I'm curious about the Google APIs and I was wondering if you could clarify something for me. Which of the Google APIs are available for free? I'm exploring the possibility of integrating some of their services into my project, but I'm on a tight budget and I need to be mindful of the costs. Could you please provide me with a list of the free Google APIs, or perhaps point me in the direction where I can find that information? Thank you in advance for your assistance.