# Microsoft.Owin.Cors

**Kind:** Service

**Source:** `Pams/API/Pams.API/Pams.API.csproj` (line 1)

**Part of:** [Pams](subsystem-pams)

NuGet package dependency

`Microsoft.Owin.Cors` is a NuGet package dependency for the Pams API project that enables Cross-Origin Resource Sharing headers in the OWIN request pipeline. It allows browser clients hosted on permitted origins to send requests to API endpoints and receive CORS-enabled responses.

## Diagram

```mermaid
sequenceDiagram
    participant Client as Browser Client
    participant API as Pams API
    participant CORS as OWIN CORS Middleware

    Client->>API: OPTIONS or API request
    API->>CORS: Process request headers
    CORS-->>API: Add allowed CORS headers
    API-->>Client: CORS-enabled response
```

## Usage

```typescript
const response = await fetch("https://api.example.com/pams/items", {
  method: "GET",
  headers: {
    Accept: "application/json",
  },
});

if (!response.ok) {
  throw new Error(`API request failed: ${response.status}`);
}

const items = await response.json();
console.log(items);
```

## AI Coding Instructions

- Configure CORS in the OWIN startup pipeline before Web API middleware handles requests.
- Restrict allowed origins, methods, and headers instead of enabling CORS for every origin unless the API contract requires it.
- Confirm that preflight `OPTIONS` requests reach the CORS middleware and are not blocked by authentication or routing.
- Keep browser client origins aligned with the API CORS policy when adding new frontend environments.

## Used by

1 reference from 1 file. Each is a place in this repository where the symbol is actually used — go read one rather than trusting an example.

### Injected or called by (1)

- `Pams.API` — `Pams/API/Pams.API/Pams.API.csproj`:1