How to Get an LLM API Key for Free (2025 Guide)

If you want to call an LLM from your own code without paying upfront, you have three realistic paths: a provider's free tier (limited requests or credits), a time-boxed free trial (credits that expire), or a local open-source model that needs no key at all. There is no provider today offering unlimited free production access to a frontier model — "free" always means a cap on volume, speed, or time.

This guide walks through where those free keys actually exist right now, how to get one in under 10 minutes, and what breaks once you try to use it for anything beyond a weekend project.

The short answer

Pick based on what you're building:

• Testing/prototyping only → Google AI Studio (Gemini) or Groq give generous free tiers with no credit card.
• Running an open-source model → Hugging Face Inference API free tier, or run it locally with Ollama (no key, no limit, but you need hardware).
• Building on Claude specifically → Anthropic's console gives trial credits at signup, then it's pay-as-you-go — no permanent free tier.
• Already paying for a Claude subscription and want an API instead of separate API billing → this is the case SubToAPI solves; more on that below.

Where free LLM API keys actually exist

Google AI Studio (Gemini)

Google currently offers the most usable free tier for a frontier-ish model. Go to aistudio.google.com, sign in with a Google account, and generate a key from "Get API key." No credit card required for the free tier. Limits are per-minute and per-day request caps that vary by model, and free-tier data may be used to improve Google's models — read the terms before sending anything sensitive.

Groq

Groq runs open-weight models (Llama, Mixtral, etc.) on custom hardware and is fast. Sign up at console.groq.com, create a key, no card needed. The free tier has token-per-minute limits that are fine for prototypes but will throttle any real traffic.

Hugging Face Inference API

Free tier gives you access to thousands of hosted open models through one API. Create an account, go to Settings → Access Tokens, generate a read token. Rate limits are tight and cold-start latency on less popular models can be several seconds.

Anthropic Claude

Anthropic's console (console.anthropic.com) gives new accounts trial credits, not a permanent free tier. Once the credits run out, you're on metered pay-as-you-go pricing per token. This is the most common point of confusion for people searching "free Claude API key" — the trial is free, ongoing usage isn't.

OpenAI

Same pattern as Anthropic: new accounts historically get a small trial credit, but OpenAI has tightened this repeatedly and in many regions now requires a card on file before any usage, free or not. Check platform.openai.com directly since terms change often.

Local models — genuinely free, no key

If "free" matters more than "hosted," run a model locally with Ollama or LM Studio. No API key, no rate limit beyond your own hardware, and no data leaves your machine. The tradeoff is you need enough RAM/VRAM to run a model at usable speed, and open-weight models generally trail Claude or GPT-4-class models on complex reasoning and long-context tasks.

# example: running a local model, no API key required
ollama pull llama3
ollama run llama3

The catch with "free" LLM API keys

Every free option above shares the same three limits:

1. Rate limits — usually requests-per-minute and tokens-per-minute low enough that a single production app hits them within minutes.
2. Model access — free tiers rarely include the newest, most capable model version; you get an older or smaller variant.
3. Data terms — some free tiers reserve the right to use your prompts for training. Read this before sending customer data or proprietary code through a free key.

None of this is a trick — it's how providers subsidize experimentation while keeping paying customers on dedicated capacity. If you're validating an idea, free tiers are the right tool. If you're shipping something people depend on, budget for real usage from day one.

A different way to get API access: use a subscription you already pay for

If you already pay for a Claude subscription and don't want a second, separate metered API bill, there's another option worth knowing about. SubToAPI turns your existing Claude access into a standard HTTPS API — you get an application key (sub_live_...), call a normal REST endpoint, and get streaming, tool use, and usage metadata without setting up token-based billing on top of what you already pay.

It's not a "free API key" in the sense of a no-cost tier — plans start at €9/month (Solo), with Team at €19/seat and Scale at €49/seat — but if you're already paying for Claude access, it avoids paying twice: once for the subscription and again per-token for API calls. There's a free trial at /signup to test it before committing.

A basic call looks like this once you have a key from the dashboard:

curl https://api.subtoapi.app/v1/messages \
  -H "Authorization: Bearer $SUBTOAPI_KEY" \
  -H "content-type: application/json" \
  -d '{
    "model": "claude-3-5-sonnet",
    "max_tokens": 1024,
    "messages": [{"role": "user", "content": "Summarize this in two sentences: ..."}]
  }'

The quickstart covers key creation and your first request end-to-end, /docs/messages documents the request/response shape, /docs/streaming covers server-sent events for streaming responses, and /docs/tools covers function/tool calling. Full plan details are on /pricing.

Choosing between free tiers and paid access

For learning, prototyping, or a side project with light traffic, a free tier from Gemini or Groq is the fastest path — you'll have a working key in minutes with no payment info. For anything you plan to keep running, plan around actual usage volume rather than the free allowance, since every provider's free tier is designed to be outgrown quickly.

questions

Is there a permanently free Claude API key? No. Anthropic gives new accounts trial credits at signup, but there's no ongoing free tier — after the trial, usage is billed per token. Gemini and Groq currently offer the closest thing to a lasting free tier among major providers.

Which free LLM API has the highest rate limits? Groq and Google AI Studio (Gemini) currently offer the most generous free-tier limits for prototyping, though exact numbers change often and vary by model — check each provider's current docs before relying on a specific figure.

Can I avoid API keys entirely and still use an LLM for free? Yes — run an open-weight model locally with Ollama or LM Studio. There's no key, no rate limit beyond your hardware, and no data sent to a third party, but you'll need enough local compute and accept that open models generally lag frontier models on hard reasoning tasks.