# Campaign API errors (/docs/developers/errors)

Status codes and the error format the Campaign API returns.

The Campaign API (v0) returns errors as JSON with a single `error` message. The Platform API uses a richer format with stable codes: see [Platform API errors](/docs/developers/platform-api#errors).

```json
{ "error": "Invalid or revoked API key." }
```

| Status | Meaning                                                                                                                             | What to do                                            |
| ------ | ----------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------- |
| `200`  | Success                                                                                                                             | —                                                     |
| `400`  | Invalid parameters — an unknown cycle, tag or group id (including ids from another brand), or a malformed date, `limit` or `cursor` | Fix the request; the message says which parameter     |
| `401`  | Missing, malformed, unknown or revoked API key                                                                                      | Check the header and that the key hasn't been revoked |
| `500`  | An unexpected error on the Bloss side                                                                                               | Retry with backoff; contact support if it persists    |

The `error` message is meant for developers, not end users — don't show it directly in your product.