---
title: "Start multipart attachment upload"
method: POST
path: "/v1/private/attachment/upload-start"
tags: ["Attachments"]
---

# Start multipart attachment upload

`POST /v1/private/attachment/upload-start`

Start multipart attachment upload

## Request body

- StartMultipartUploadRequest
  - `file_name` string, required
  - `num_of_file_parts` integer, required
  - `mime_type` string
  - `project_name` string — If null, the default project is used
  - `entity_type` 'trace' | 'span', required
  - `entity_id` string, uuid, required
  - `container_id` string, uuid
  - `path` string, required

## Response `200`

MultipartUploadResponse

- StartMultipartUploadResponse
  - `upload_id` string, required
  - `pre_sign_urls` string[], required

## Other responses

- `401` — Bad Request
- `403` — Access forbidden

---

[API](https://skmtc.net/comet-ml/apis/opik-rest-api.md) · [All operations](https://skmtc.net/comet-ml/apis/opik-rest-api/llms.txt) · [OpenAPI document](https://skmtc-service-staging.skmtc.workers.dev/v1/apis/comet-ml/opik-rest-api/versions/4ed2fbc97cc3/schema)