> ## Documentation Index
> Fetch the complete documentation index at: https://ngrok.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Restrict providers and models

> Limit which providers and models an access key can call.

Use access key configurations to control which providers and models an access key can call.

Restrictions are checked before the gateway routes a request upstream. That means a request can fail fast if a client asks for a provider or model the key shouldn't use.

## What you'll need

* An [access key](/ai-gateway/concepts/access-keys).
* An [access key configuration](/ai-gateway/guides/access-key-configurations).
* The provider IDs and model IDs you want to allow.

## Allow specific providers

Use provider restrictions when an access key should only call certain providers.

```json theme={null}
{
  "access": {
    "providers": {
      "allow": ["openai", "anthropic"]
    }
  }
}
```

With this configuration, requests can only route to OpenAI or Anthropic.

## Allow specific models

Use model restrictions when an access key should only call certain models.

```json theme={null}
{
  "access": {
    "models": {
      "allow": ["openai/gpt-4o", "anthropic/claude-sonnet-4-6"]
    }
  }
}
```

Use the provider and model in the access rule so the gateway knows exactly which upstream model is allowed.

## Allow providers and models together

Combine provider and model restrictions when you want a key to stay within a small set of approved providers and models.

```json theme={null}
{
  "access": {
    "providers": {
      "allow": ["openai", "anthropic"]
    },
    "models": {
      "allow": ["openai/gpt-4o", "anthropic/claude-sonnet-4-6"]
    }
  }
}
```

Requests outside the allowed providers or models are rejected before they reach an upstream provider.

## How this works with fallback

Every model in a fallback request must be allowed.

```json theme={null}
{
  "model": "openai:gpt-4o",
  "models": ["anthropic:claude-sonnet-4-6"],
  "messages": [{"role": "user", "content": "Hello"}]
}
```

If the primary model is allowed but the fallback model is not, the fallback model can't be used.

## Common patterns

| Goal                                | Configuration                              |
| ----------------------------------- | ------------------------------------------ |
| Allow only OpenAI                   | Allow provider `openai`                    |
| Allow only Claude Sonnet            | Allow model `anthropic/claude-sonnet-4-6`  |
| Give a team access to two providers | Allow both provider IDs                    |
| Block expensive models              | Allow only approved model IDs              |
| Limit a custom provider             | Allow the custom provider ID and model IDs |

## Next steps

* [Access key configurations](/ai-gateway/guides/access-key-configurations): Full configuration flow
* [Choose a model](/ai-gateway/guides/model-selection-strategies): Use model IDs in requests
* [Configure fallback models](/ai-gateway/guides/configure-fallback-models): Use allowed fallback models