> For the complete documentation index, see [llms.txt](https://bountyv.gitbook.io/vdocs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bountyv.gitbook.io/vdocs/account/uploads-sign.md).

# Signed uploads

Get a presigned URL you can `PUT` a large file to directly, bypassing the platform's request body size limit — then hand the resulting public URL to whichever endpoint needs it (e.g. `video_url` on [Wan Reel](/vdocs/video-api/videos-wan-reel.md), `reference_video_url` on [Reel Recreate](/vdocs/video-api/videos-generate.md), or `image_urls` on [Seedance](/vdocs/frontier-passthrough/frontier-seedance.md)).

```
POST /api/v1/uploads/sign
```

Synchronous — the call immediately returns a signed URL. Uploading the file to that URL is a separate step you perform right after (see below).

## Authentication

Requires a Bearer API key. See [Authentication](/vdocs/authentication.md).

## Request

**Content-Type:** `application/json`

| Field          | Type   | Required | Default    | Description                                                              |
| -------------- | ------ | -------- | ---------- | ------------------------------------------------------------------------ |
| `filename`     | string | —        | `"upload"` | Original filename. Only the extension is used, to name the stored object |
| `content_type` | string | —        | —          | Accepted in the body but not currently used by the server                |

## Response

```json
{
  "upload_url": "https://<project>.supabase.co/storage/v1/object/upload/sign/uploads/api-uploads/usr_123/direct/V1StGXR8_Z5jdHi6B-myT.mp4?token=...",
  "public_url": "https://<project>.supabase.co/storage/v1/object/public/uploads/api-uploads/usr_123/direct/V1StGXR8_Z5jdHi6B-myT.mp4",
  "storage_path": "api-uploads/usr_123/direct/V1StGXR8_Z5jdHi6B-myT.mp4"
}
```

| Field          | Type   | Description                                                                   |
| -------------- | ------ | ----------------------------------------------------------------------------- |
| `upload_url`   | string | One-time signed URL — `PUT` your file's bytes here                            |
| `public_url`   | string | Permanent public URL — pass this to other endpoints once the upload completes |
| `storage_path` | string | Internal storage path (informational; you generally don't need it)            |

HTTP status: `200 OK`.

## The full flow

1. **Sign** — call `POST /api/v1/uploads/sign` with a `filename` to get `upload_url` and `public_url`.
2. **Upload** — `PUT` the raw file bytes to `upload_url`. This request goes straight to storage, not through the Substance API, so it isn't subject to the API's body size limit.
3. **Use** — pass `public_url` as the URL field on whichever endpoint accepts it — for example `video_url` on [Wan Reel](/vdocs/video-api/videos-wan-reel.md), `reference_video_url` on [Reel Recreate](/vdocs/video-api/videos-generate.md), `image_urls` on [Seedance](/vdocs/frontier-passthrough/frontier-seedance.md), or `audio_url`/`image_url` on [Lyric Video](/vdocs/youtube-tools-api/lyric-video.md) / [Music Short](/vdocs/youtube-tools-api/music-short.md).

The uploaded object is stored in a public bucket, so `public_url` is fetchable by our workers (and by anyone else who has the link) as soon as the `PUT` completes — treat it like any other public file URL. See [Uploading Files](/vdocs/uploading-files.md) for the size/format requirements that apply to each downstream endpoint's own inputs.

## Example

```bash
# 1. Sign
curl -X POST https://substance-api.com/api/v1/uploads/sign \
  -H "Authorization: Bearer sk_live_..." \
  -H "Content-Type: application/json" \
  -d '{"filename": "my-reel.mp4"}'

# => { "upload_url": "...", "public_url": "...", "storage_path": "..." }

# 2. Upload the file to the signed URL
curl -X PUT "<upload_url from step 1>" \
  --upload-file ./my-reel.mp4

# 3. Use the public_url with another endpoint, e.g. Wan Reel
curl -X POST https://substance-api.com/api/v1/videos/wan-reel \
  -H "Authorization: Bearer sk_live_..." \
  -F "face=@face.jpg" \
  -F "video_url=<public_url from step 1>"
```

```javascript
import { readFileSync } from "node:fs";

const sign = await fetch("https://substance-api.com/api/v1/uploads/sign", {
  method: "POST",
  headers: {
    Authorization: `Bearer ${API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({ filename: "my-reel.mp4" }),
});
const { upload_url, public_url } = await sign.json();

await fetch(upload_url, {
  method: "PUT",
  body: readFileSync("./my-reel.mp4"),
});

// public_url is now ready to pass to another endpoint
```

## Errors

| Status | When                                                   |
| ------ | ------------------------------------------------------ |
| `400`  | Request body isn't valid JSON                          |
| `401`  | Missing, malformed, or revoked API key                 |
| `403`  | Account disabled — contact support                     |
| `429`  | Rate limit exceeded for your key                       |
| `500`  | Could not create the signed upload URL — safe to retry |

`PUT`-ing to an expired or already-used `upload_url` fails at the storage layer — request a fresh one via this endpoint rather than retrying the same `upload_url`.

See [Errors](/vdocs/errors.md) for the full error format.

## Pricing

Free — this endpoint is not billed.


---

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