Seedance 2.0 Fast API
ByteDancevideo$0.869 / runSubmit 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.
- 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 $EZFLOWS_API_KEY" \ -H "Content-Type: application/json" \ -d '{ "prompt": "a wide shot of a desert at dusk", "duration": 5, "aspect_ratio": "16:9" }' # 202 Accepted, at once — it never waits for the model: # {"request_id": "req_8f2a41c9b70e4d15", "status": "queued", # "poll_url": "https://api.ezflows.io/v1/requests/req_8f2a41c9b70e4d15"} - 02
Poll
Same bearer header, every few seconds, until the status is final.
curlGET /v1/requests/:id REQUEST_ID=req_8f2a41c9b70e4d15 # from the POST while :; do BODY=$(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 - 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" } ] } } } - 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
| Name | Type | Default | Allowed | Description |
|---|---|---|---|---|
| promptrequired | string | — | — | 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_url | string | — | one image url | Image URL to anchor the starting frame; mutually exclusive with reference_images. Best for product shots and character-led scenes. |
| last_frame_url | string | — | one image url | Image URL to define the final frame; requires first_frame_url set. Use for scene transitions or story resolution. |
| reference_images | string[] | — | up to 9 image urls | Up to 9 image URLs for style or character consistency; cite as image 1 in prompt. Fewer references yield stronger influence. |
| reference_videos | string[] | — | up to 3 video urls | Up 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_audios | string[] | — | up to 3 audio urls | Up 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. |
| duration | enum | 5 | 4 · 5 · 6 · 7 · 8 · 9 · 10 · 11 · 12 · 13 · 14 · 15 | Video length in seconds: 4, 5, 6, 8, 10, 12, or 15; -1 for auto. Use 5s for social posts, 10-15s for product demos. |
| resolution | enum | 720p | 480p · 720p | Output resolution: 720p recommended for production; 480p for faster previews or low-bandwidth delivery. |
| aspect_ratio | enum | 16:9 | 16:9 · 9:16 · 1:1 · 4:3 · 3:4 · 21:9 | Output dimensions: 16:9 for widescreen, 9:16 for mobile Reels, 1:1 for feed posts, 21:9 for cinematic. |
| generate_audio | boolean | true | — | Enable native audio co-generation (dialogue, SFX, ambient, music); set true for final delivery, false for draft iterations. |
| seed | integer | -1 | -1–2147483647 | Integer for reproducible output; -1 generates a new random seed each run. Fix seed when iterating on prompt changes. |
| return_last_frame | boolean | false | — | Return the final frame as a separate image URL; useful for chaining clips or extracting scene-end stills. |
| bitrate_mode | enum | standard | standard · high | Output 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_resize | boolean | true | — | 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.