# CORS And Responses

Use the gateway CORS block to centralize browser access policy instead of reimplementing it in every upstream.

**Last reviewed:** 2026-03-06

## When to use this

Use this approach when you want a config-first Cloudflare Worker gateway behavior that is already implemented in the repository and covered by tests or canonical examples.

## What this does not do

* It does not add unsupported product features such as rate limiting, caching, API keys, analytics, or OpenAPI generation.
* It does not replace upstream application logic that still belongs in your services.
* It does not remove the need to validate environment variables, bindings, and route intent before deploy.

## Repo-grounded example

```json
{
  "cors": {
    "allow_origins": ["https://app.example.com"],
    "allow_methods": ["GET", "POST", "OPTIONS"],
    "allow_headers": ["Content-Type", "Authorization", "X-Refresh-Token"],
    "expose_headers": ["X-Request-Id"],
    "allow_credentials": true,
    "max_age": 300
  }
}
```

This example is grounded in the current implementation shape: JSON config, path-based routing, optional auth, request mapping, and Worker-native integrations.

## Troubleshooting

* Confirm the route path and HTTP method match what the worker receives.
* Confirm the config source is the one you expect: local file, KV, or `SAG_API_CONFIG_JSON`.
* Confirm required bindings and environment variables are present before debugging downstream logic.
* Run the existing tests in the main gateway repo when a config change appears correct but runtime behavior disagrees.

## Related docs

* [cors](https://docs.serverlessapigateway.com/configuration/cors)
* [introduction](https://docs.serverlessapigateway.com/getting-started/introduction)
* [gateway troubleshooting matrix](https://docs.serverlessapigateway.com/troubleshooting/wrangler-deploy-guide/gateway-troubleshooting-matrix)