# format-unknown

The request names a **format that SynthEvents does not write**.

- **Status:** `422 Unprocessable Entity`
- **Routes:** `POST /api/v1/generate-events`, `QUERY /api/v1/read-data-set`
- **Description:** `format is unknown: expected 'cloudevents' or 'eventsourcingdb'`
- **Details:** **`value`**, the format as the request gave it.

## Why It Happens

The value of `format` is neither `cloudevents` nor `eventsourcingdb`. Names are lowercase and exact, so `CloudEvents` is unknown.

## How to Fix It

Use `cloudevents` for plain CloudEvents, or `eventsourcingdb` for a backup for EventSourcingDB (see **[Formats](/docs/synthevents/formats)**).

## Example

For the format `json`, SynthEvents answers:

```json
{
  "type": "error",
  "data": {
    "code": "https://docs.synthevents.io/errors/format-unknown",
    "description": "format is unknown: expected 'cloudevents' or 'eventsourcingdb'",
    "details": {
      "value": "json"
    }
  }
}
```