Any free LLM APIs for beginners to test and learn without needing a credit card?

Hi everyone,
I’m just getting started with learning about LLMs and concepts like Retrieval-Augmented Generation (RAG). As a beginner, I want to experiment and get hands-on experience, but I’ve run into an issue i.e. most APIs (like OpenAI’s GPT or Anthropic’s Claude) require an API key and to get that, you usually need to add a credit card. Are there any LLM APIs or platforms that let beginners try things out for free, without needing a credit card? I’m not looking to run large-scale models, just something I can use to test and learn the basics. Would really appreciate any beginner-friendly suggestions or alternatives!