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Authentication identifies the caller; the selected model, route and features determine what usage is free or chargeable.
The phrase free OpenRouter API key often combines two questions: obtaining credentials and paying for calls. A key provides authentication; a free model and its restrictions must be checked separately. Creating a new secret does not make a paid model free, expand shared limits or reserve compute for an application.
Separate access from execution
Authentication tells the service whose application is making the request. Model usage follows the conditions of the selected model, provider and enabled features. Keep those decisions in separate fields in the pilot record rather than labelling the entire integration free because the key was easy to create.
Assign the credential an owner, application and environment. Keep it on the authorized server side and define how to revoke it after the test. These operational requirements remain relevant when a particular model entry has no token charge.
Choose a documented free mode
Check the current pricing and model catalog for an existing eligible free entry or the documented free router. Do not add a suffix to an arbitrary model name and assume the service has created a corresponding free endpoint. Record the exact API identifier that the application sends.
A successful call also needs a capability check. Text generation does not establish support for the application’s required tools, schema or input length. Treat missing features as an explicit test outcome. Current eligibility and payment options remain account- and location-dependent; the key alone does not settle them.
Write down the experiment’s limits
| Question | What to record |
|---|---|
| Which model or router is used? | Exact API identifier |
| Which request restrictions apply? | The current account rule |
| Is a paid backup allowed? | An explicit test decision and spending boundary |
| Who owns the credential? | Responsible person and application |
Use a small fixed dataset, short output allowance and finite waiting period. Save task identifiers so that an interrupted case can be repeated deliberately. Unbounded retries can consume allowance without producing a useful conclusion about the workflow.
Verify one call and define completion
Make a short, non-sensitive request and inspect the returned model, content, finish state and usage. Keep failures separate from incorrect answers. If a fallback responds, determine whether it changed the cost or model assumptions instead of counting it automatically as a free success.
Decide when the experiment is complete: for example, when the fixed cases have either finished or reached their deadlines. Summarize quality and availability under those conditions without extrapolating to permanent capacity. That creates a separate, measurable basis for discussing local compute.
Official references: openrouter.ai — authentication, openrouter.ai — pricing.
Related guides: Setting up an OpenRouter API key for an application, OpenRouter free model router: checking which model answered.