Overview

OpenRouter is a model-routing platform that lets you reach many vendors' models with a single API key. It maintains a set of models marked as free, usually with tighter rate limits — good for experiments, not heavy workloads.

Steps

  1. Sign up at openrouter.ai.
  2. Create an API key on the Keys page and optionally set a spend cap.
  3. Filter the model list for :free models and copy the model ID.
  4. Call it in OpenAI-compatible format, pointing the base URL at OpenRouter's endpoint.
  5. Watch response headers and the usage page to see whether you hit limits.

Caveats

  • Free model availability changes with provider policies and can be retired or renamed at any time.
  • The free tier usually has daily request and concurrency limits; exceeding them returns error codes.
  • Some free models may log requests for training, so avoid sensitive data.
  • Don't use multiple accounts to bypass limits — that may violate the terms.

Best for

Model comparisons, A/B tests, cost-controlled learning, open-source demos.

2026 timeliness note

Free model lists change often; rely on the live tags on the platform's model page.