---
raw: true
title: "upload_chunk_invalid"
description: "Chunk contents are not canonical base64."
---

Chunk contents are not canonical base64.

**How to resolve:** Encode the exact bytes as padded standard base64, or use utf8.

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## Error shape

Every Spacefast API error is an RFC 9457 problem document, served as
`application/problem+json`.

- `code` is stable and machine-readable.
- `type` links to this page.
- `title` is a short label.
- `status` repeats the HTTP status.
- `detail` explains this occurrence.
- `pointer`, when present, is an RFC 6901 JSON Pointer at the offending field in the request body.
- `details`, when present, carries structured context.

Match on `code`, never on `detail`.

```json
{
  "type": "https://spacefast.com/docs/errors/upload_chunk_invalid/",
  "title": "Upload chunk invalid",
  "status": 400,
  "detail": "Chunk contents are not canonical base64.",
  "code": "upload_chunk_invalid",
  "requestId": "req_4mz0v8qk"
}
```

See the full list of error codes in the [error reference](/docs/errors/).

</div>