Seedance 2.0 Fast API

ByteDancevideo$0.869 / run

Submit a Seedance 2.0 Fast run over HTTP, then poll it or take a webhook. Results are files on media.ezflows.io. Try it in the playground first.

Async: the POST answers at once with a request id. Poll it, or take the webhook.

  1. 01

    Submit

    Parameters at the top level of the JSON body. Answers 202 with a request id.

    curlPOST /v1/models/seedance-2.0-fast
    curl -X POST https://api.ezflows.io/v1/models/seedance-2.0-fast \
      -H "Authorization: Bearer $EZFLOWS_API_KEY" \
      -H "Content-Type: application/json" \
      -d '{
        "prompt": "a wide shot of a desert at dusk",
        "duration": 5,
        "aspect_ratio": "16:9"
      }'
    
    # 202 Accepted, at once — it never waits for the model:
    # {"request_id": "req_8f2a41c9b70e4d15", "status": "queued",
    #  "poll_url": "https://api.ezflows.io/v1/requests/req_8f2a41c9b70e4d15"}
  2. 02

    Poll

    Same bearer header, every few seconds, until the status is final.

    curlGET /v1/requests/:id
    REQUEST_ID=req_8f2a41c9b70e4d15   # from the POST
    
    while :; do
      BODY=$(curl -s https://api.ezflows.io/v1/requests/$REQUEST_ID \
        -H "Authorization: Bearer $EZFLOWS_API_KEY")
      STATUS=$(echo "$BODY" | jq -r .data.status)
      case "$STATUS" in succeeded|failed|cancelled) break ;; esac
      sleep 3
    done
    
    echo "$BODY" | jq -r '.data.output.artifacts[].url'   # media.ezflows.io, kept 90 days
  3. 03

    Response

    Files are on media.ezflows.io, kept 90 days. A failed run says why and costs nothing.

    json200 · succeeded
    {
      "data": {
        "id": "req_8f2a41c9b70e4d15",
        "model_slug": "seedance-2.0-fast",
        "status": "succeeded",
        "http_status": 200,
        "cost": 0.868653,
        "auth_method": "api_key",
        "error": null,
        "submitted_at": "2026-09-12T18:07:21.114Z",
        "queue_started_at": "2026-09-12T18:07:21.402Z",
        "execution_started_at": "2026-09-12T18:07:22.010Z",
        "first_byte_at": "2026-09-12T18:07:52.871Z",
        "finished_at": "2026-09-12T18:07:55.203Z",
        "io_deleted_at": null,
        "canvas_id": null,
        "canvas_node_id": null,
        "client_attempt_id": null,
        "idempotency_key": null,
        "input": {
          "prompt": "a wide shot of a desert at dusk",
          "duration": 5,
          "aspect_ratio": "16:9"
        },
        "output": {
          "artifacts": [
            {
              "index": 0,
              "kind": "video",
              "contentType": "video/mp4",
              "url": "https://media.ezflows.io/outputs/<account>/req_8f2a41c9b70e4d15/0.mp4"
            }
          ]
        }
      }
    }
  4. 04

    Webhook

    Skip polling: we POST the result to your endpoint, at least once.

    Register
    Create an endpoint under Webhooks in the dashboard; the signing secret is shown once.
    Events
    request.succeeded · request.failed · request.cancelled
    Headers
    ezflows-event-id (dedupe on it) · ezflows-timestamp (unix seconds) · ezflows-signature t=<ts>,v1=<hex HMAC-SHA256 of "<ts>.<raw body>">
    Verify
    Over the exact bytes received, in constant time; reject anything older than five minutes.
    Respond
    Any 2xx within 10 s. Redirects are not followed.
    Retries
    Five, with backoff: 30 s · 60 s · 2 min · 4 min · 8 min. Disabled after five consecutive dead deliveries.
    jsonDelivery body
    {
      "id": "82cf46a4-841e-41d6-b3c7-facc937d3252",
      "type": "request.succeeded",
      "created_at": "2026-09-12T18:07:55Z",
      "data": {
        "id": "req_8f2a41c9b70e4d15",
        "model_slug": "seedance-2.0-fast",
        "status": "succeeded",
        "cost": 0.868653,
        "output": {
          "artifacts": [
            {
              "url": "https://media.ezflows.io/…/0.mp4"
            }
          ]
        }
      }
    }
    curlverify.sh
    # Create the endpoint under Webhooks in the dashboard; the signing secret is shown once.
    # ezflows-signature: t=<ts>,v1=<hex HMAC-SHA256 of "<ts>.<raw body>">
    # body.json = the exact bytes received. Reject anything older than five minutes.
    EXPECTED=$({ printf '%s.' "$TS"; cat body.json; } \
      | openssl dgst -sha256 -hmac "$EZFLOWS_WEBHOOK_SECRET" -r | cut -d' ' -f1)
    
    [ "$EXPECTED" = "$V1" ] && echo "valid" || echo "reject"

Parameters 14

NameTypeDefaultAllowedDescription
promptrequiredstring——Describe the video scene; use Shot 1: / Shot 2: for multi-shot or image 1 / video 1 for omni-reference. Best for cinematic narration or product demos.
first_frame_urlstring—one image urlImage URL to anchor the starting frame; mutually exclusive with reference_images. Best for product shots and character-led scenes.
last_frame_urlstring—one image urlImage URL to define the final frame; requires first_frame_url set. Use for scene transitions or story resolution.
reference_imagesstring[]—up to 9 image urlsUp to 9 image URLs for style or character consistency; cite as image 1 in prompt. Fewer references yield stronger influence.
reference_videosstring[]—up to 3 video urlsUp to 3 reference videos (2-15 seconds each) for motion/style transfer. Cite as 'video 1' in your prompt. Requests with reference videos are billed at the video-to-video token rate.
reference_audiosstring[]—up to 3 audio urlsUp to 3 reference audio files (MP3). Cite as 'audio 1' in your prompt. Cannot be used with text+audio only — include an image or video input too.
durationenum54 · 5 · 6 · 7 · 8 · 9 · 10 · 11 · 12 · 13 · 14 · 15Video length in seconds: 4, 5, 6, 8, 10, 12, or 15; -1 for auto. Use 5s for social posts, 10-15s for product demos.
resolutionenum720p480p · 720pOutput resolution: 720p recommended for production; 480p for faster previews or low-bandwidth delivery.
aspect_ratioenum16:916:9 · 9:16 · 1:1 · 4:3 · 3:4 · 21:9Output dimensions: 16:9 for widescreen, 9:16 for mobile Reels, 1:1 for feed posts, 21:9 for cinematic.
generate_audiobooleantrue—Enable native audio co-generation (dialogue, SFX, ambient, music); set true for final delivery, false for draft iterations.
seedinteger-1-1–2147483647Integer for reproducible output; -1 generates a new random seed each run. Fix seed when iterating on prompt changes.
return_last_framebooleanfalse—Return the final frame as a separate image URL; useful for chaining clips or extracting scene-end stills.
bitrate_modeenumstandardstandard · highOutput video encoding bitrate. 'standard' gives smaller files and faster downloads; 'high' produces ~5-6x higher bitrate for better visual fidelity and fewer compression artifacts (larger files). Does not affect price.
auto_resizebooleantrue—Automatically resizes an input image that falls outside the provider's accepted range (300-6000px per side, aspect ratio 0.4-2.5, 30MB) so the request succeeds instead of being rejected. Aspect ratio is preserved: oversized images are downscaled, undersized ones upscaled, and out-of-band ratios padded rather than cropped. On by default - set it to false to have the provider reject out-of-range images instead. When a resize happens the response carries an X-Input-Normalized header naming the field and the before/after dimensions.

File inputs (first_frame_url: one image url · last_frame_url: one image url · reference_images: up to 9 image urls · reference_videos: up to 3 video urls · reference_audios: up to 3 audio urls) take URLs. Upload the raw file to POST /v1/uploads with its own Content-Type and pass the url it returns. Inputs are kept 90 days.