Why Start Here?
Large Language Models are powerful, but getting started can feel overwhelming. This guide cuts through the noise: you'll pick a free API provider, paste in your key, and talk to an AI model — all in your browser.
⏱️ You'll have a working LLM call in under 10 minutes. No credit card required.
Get a Free API Key
Use OpenRouter with its Free Models Router. It picks an available free model for you, so this guide has only one path to follow — no provider comparison, no model shopping.
OpenRouter · Free Models Router
The OpenRouter Free Models Router routes your request to an available free model automatically. Create a free OpenRouter key, paste it below, and keep the model set to Free Models Router.
Get API Key →Your First LLM Call
Enter your API key above, type a message, and hit Send
This playground intentionally only offers the OpenRouter Free Models Router, so beginners do not have to compare providers or pick model IDs.
Your API key and messages are sent directly from your browser to OpenRouter. The guide server does not receive the key. This page keeps it in memory and clears it when you leave or reload.
Verify in source code ↗curl https://openrouter.ai/api/v1/chat/completions \
-H "Content-Type: application/json" \
-H "Authorization: Bearer YOUR_API_KEY" \
-d '{
"model": "openrouter/free",
"messages": [{"role": "user", "content": "Hello, who are you?"}],
"temperature": 0.7,
"max_tokens": 256
}'Understanding the Response
choices[0].message.content
The actual text the model generated. This is what you'd show to a user.
usage.prompt_tokens / completion_tokens
How many tokens were used. Prompt tokens = your input, completion tokens = the model's output. This is how billing works (though free tiers don't charge).
finish_reason
"stop" means the model finished naturally. "length" means it hit the max_tokens limit and was cut off.
model
The exact model that processed your request. Some providers may route to different versions.
Your Learning Path
A curated roadmap from zero to advanced. Follow these topics in order for the best learning experience.
Learn the fundamentals of talking to AI models effectively
See how sampling changes token probabilities
See how text gets broken into tokens the model understands
The building blocks behind every AI model
How models see and understand images
Run AI models on your own machine
Next Steps
Now that you've made your first LLM call, explore these topics to go deeper: