> ## Documentation Index
> Fetch the complete documentation index at: https://autorender.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Multipart start
> Create a multipart session and receive part size plus presigned PUT URLs.
```bash cURL theme={null}
curl --request POST \
--url https://upload.autorender.io/api/v1/multipart/start \
--header 'Authorization: Bearer YOUR_API_KEY' \
--header 'Content-Type: application/json' \
--data '{
"file_name": "big-video.mp4",
"size": 73400320,
"format": "video/mp4",
"folder": "uploads/videos",
"tags": ["campaign", "raw"],
"metadata": { "source": "mobile-app" },
"custom_id": "vid_001",
"random_prefix": false,
"ttl_seconds": 3600
}'
```
```json 200 theme={null}
{
"session_id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
"part_size": 10485760,
"parts": [
"https://storage.example.com/presigned-part-1?X-Amz-Signature=abc",
"https://storage.example.com/presigned-part-2?X-Amz-Signature=def"
]
}
```
```json 400 theme={null}
{
"success": false,
"error": ""
}
```
```json 401 theme={null}
{
"success": false,
"error": "Unauthorized",
"message": "Invalid or missing API key"
}
```
```json 500 theme={null}
{
"success": false,
"error": "",
"message": ""
}
```
## Overview
Starts a multipart upload for large files. The response gives you `session_id`, **`part_size`** (the chunk size in bytes), and **`parts`** (presigned URLs, in order). Upload each chunk with [Upload parts](/docs/api-reference/multipart-upload-parts), then finalize with [Multipart complete](/docs/api-reference/multipart-complete).
## Authentication
`Authorization: Bearer YOUR_API_KEY`
## Workflow
This is **step 1 of 3**.
1. **Multipart start** (this endpoint) — get `session_id`, `part_size`, and `parts`.
2. [**Upload parts**](/docs/api-reference/multipart-upload-parts) — `PUT` each chunk to the matching presigned URL.
3. [**Multipart complete**](/docs/api-reference/multipart-complete) — finalize the file in your workspace.
## Request body
| Field | Type | Required | Description |
| --------------- | --------- | -------- | ------------------------------------------ |
| `file_name` | string | Yes | Original file name (e.g. `big-video.mp4`) |
| `size` | number | Yes | Total file size in bytes |
| `format` | string | Yes | MIME type (e.g. `video/mp4`, `image/jpeg`) |
| `folder` | string | No | Workspace folder path |
| `tags` | string\[] | No | Tags |
| `metadata` | object | No | Custom metadata |
| `custom_id` | string | No | Your tracking id |
| `random_prefix` | boolean | No | Random prefix on stored name if `true` |
| `ttl_seconds` | number | No | Lifetime of the presigned URLs, in seconds |
## Response
Returns `session_id`, `part_size`, and `parts`. Part index `i` must be uploaded to `parts[i]`.
## OpenAPI
````yaml api-reference/openapi.json POST /api/v1/multipart/start
openapi: 3.0.0
info:
title: AutoRender Public API
description: >-
REST API for uploading, managing, and serving media assets. All endpoints
require an API key via the x-api-key header or Authorization: Bearer .
version: 1.0.0
contact:
name: AutoRender Support
email: support@autorender.io
servers:
- url: https://app-api.autorender.io
description: Production server
security:
- apiKey: []
tags:
- name: Uploads
description: Upload endpoints (API key required)
- name: Files
description: File management endpoints (API key required)
- name: Folders
description: Folder management endpoints (API key required)
paths:
/api/v1/multipart/start:
post:
tags:
- Uploads
summary: Start multipart upload
description: Initialise a multipart upload session and receive pre-signed part URLs.
operationId: multipartStart
requestBody:
required: true
content:
application/json:
schema:
type: object
properties:
file_name:
type: string
minLength: 1
size:
type: integer
minimum: 1
maximum: 9007199254740991
format:
type: string
minLength: 1
folder:
type: string
tags:
anyOf:
- type: array
items:
type: string
- type: string
metadata:
type: object
additionalProperties:
x-stainless-any: true
custom_id:
type: string
random_prefix:
type: boolean
ttl_seconds:
type: integer
minimum: 1
maximum: 9007199254740991
required:
- file_name
- size
- format
responses:
'201':
description: Session created
content:
application/json:
schema:
type: object
properties:
session_id:
type: string
uuid:
type: string
part_size:
type: integer
minimum: -9007199254740991
maximum: 9007199254740991
min_part_size:
type: integer
minimum: -9007199254740991
maximum: 9007199254740991
parts:
type: array
items:
type: string
description: Pre-signed S3 upload URLs, one per part
expire_at:
type: integer
minimum: -9007199254740991
maximum: 9007199254740991
description: Unix timestamp when the session expires
public_key:
type: string
workspace_id:
type: string
policy:
type: object
properties:
folder:
type: string
tags:
type: array
items:
type: string
size:
type: integer
minimum: -9007199254740991
maximum: 9007199254740991
format:
type: string
required:
- folder
- tags
- size
- format
additionalProperties: false
required:
- session_id
- uuid
- part_size
- min_part_size
- parts
- expire_at
- public_key
- workspace_id
- policy
additionalProperties: false
description: Session created
'400':
description: Invalid request
content:
application/json:
schema:
type: object
properties:
success:
type: boolean
error:
type: string
errorCode:
type: string
message:
type: string
required:
- error
additionalProperties: false
description: Invalid request
'401':
description: Unauthorized
content:
application/json:
schema:
type: object
properties:
error:
type: string
message:
type: string
required:
- error
additionalProperties: false
description: Unauthorized
'402':
description: Storage limit exceeded
content:
application/json:
schema:
type: object
properties:
success:
type: boolean
error:
type: string
errorCode:
type: string
message:
type: string
required:
- error
additionalProperties: false
description: Storage limit exceeded
'429':
description: Rate limit exceeded
content:
application/json:
schema:
type: object
properties:
error:
type: string
message:
type: string
retryAfterSeconds:
type: number
required:
- error
- message
additionalProperties: false
description: Rate limit exceeded
'500':
description: Server error
content:
application/json:
schema:
type: object
properties:
success:
type: boolean
error:
type: string
errorCode:
type: string
message:
type: string
required:
- error
additionalProperties: false
description: Server error
security:
- apiKey: []
components:
securitySchemes:
apiKey:
type: apiKey
name: x-api-key
in: header
description: >-
API key for public endpoints. Can also be provided via Authorization:
Bearer
````