What 'free' usually means — and what it should mean
Search for a free LLM API and you mostly find two things: a trial balance that expires in a week, or a single tiny model with no path to anything bigger. Neither lets you actually build.
A free tier worth using has three properties: real models you'd ship with, a standard API so your code isn't throwaway, and a way to keep the cost at zero as usage grows instead of a cliff at the end of a trial.
Three durable ways to stay at zero
The most reliable approach combines a hosted free tier with your own provider quota. You can mix all three:
- A free model tier — route to free-tier models with a daily request allowance and no spend required.
- Starter credit — a small one-time credit (AnyRouter gives every new account $2, no card on file) usable across the whole catalog.
- Bring your own keys — if you already pay a provider directly, route on your own keys through the gateway at $0 markup and pay only what the provider charges.
The third point is the one people miss: many providers (for example Google AI Studio for Gemini) have generous free tiers of their own. Routing those keys through a gateway gives you unified billing, logs, and failover on top of a free upstream.
One endpoint, OpenAI-compatible
A free API is only useful if it's easy to call. An OpenAI-compatible endpoint means any existing client works — you just set the base URL and a key.
curl https://anyrouter.dev/v1/chat/completions \
-H "Authorization: Bearer sk-ar-v1-..." \
-H "Content-Type: application/json" \
-d '{
"model": "anyrouter/free",
"messages": [{"role": "user", "content": "Hello from a free LLM API"}]
}'Swap `anyrouter/free` for any of the 150+ `provider/model` ids when you want a bigger model — your starter credit or your own keys cover those, and nothing in your code changes.