# invalid_external_id

**The external_id of a batch operation is invalid.**

| | |
|---|---|
| HTTP status | `400` |
| `code` | `invalid_external_id` |
| Retry? | No, fix the request first |

## What it means

Only appears as the result of a single operation in a [batch](https://docs.kalender-sync.de/en/api/batch/), not as the answer to the whole call. The `external_id` must be 1 to 128 characters long and may only contain letters, digits and `.` `_` `:` `-`. On a single PUT an invalid id leads to `invalid_request`.

## How to fix it

Build the id from allowed characters, for example `wp-1482` instead of `wp 1482` or `wp/1482`.

## Example (batch result)

```json
{
  "results": [
    {
      "external_id": "wp 1482",
      "status": 400,
      "error": {
        "code": "invalid_external_id"
      }
    }
  ]
}
```

→ [All error codes](https://docs.kalender-sync.de/en/api/errors/)