Seedance 2.0 Fast – Flux1 AI API

POST/api/v1/generations

JSON requestAsynchronousOne video per request

Price is resolution rate × whole seconds. The example shows the total for its duration. Reference images do not add an extra charge. Check credits_refunded to confirm a refund; unresolved submissions may require review.

Jump to request examples ↓

Authorization

Authorizationstringrequired

Bearer fx1_live_… — send your API key in the request header. Requires administrator approval and a completed paid purchase; new generations also require enough credits.

Idempotency-Keystringoptional

Use one unique value per generation and reuse it with the same body on retries. Printable ASCII, no spaces. A different body with the same key returns 409.

Maximum length: 128 characters

Manage API keys ↗

Request body

modelstringrequired

Use this exact model ID in the top-level request body.

seedance-2-fast

promptstringrequired

Video description, 3–2,000 characters after trimming.

Maximum length: 2,000 characters

first_frame_urlstringoptional

Optional public HTTPS image URL (JPEG, PNG or WebP). Omit for text-to-video. Maximum URL length 2,048 characters.

last_frame_urlstringoptional

Optional last-frame HTTPS image URL; requires first_frame_url. Reference video/audio and mixed reference modes are not accepted.

aspect_ratiostringoptional

Output width-to-height ratio.

Default: 16:9

16:94:31:13:49:1621:9

resolutionstringoptional

Resolution determines the per-second rate. 1080p/4K are not available through this API.

Default: 720p

480p720p

durationnumberoptional

Whole seconds, 4–15 inclusive. Cost is the per-second rate multiplied by this value. Automatic duration (-1) is not accepted.

Default: 5

Range: 4–15. See field description for allowed values.

generate_audiobooleanoptional

Generate audio with the video. Both audio settings use the same displayed rate.

Default: true

Response & next step

A successful submission returns 202 and a generation id. Poll GET /api/v1/generations/{id} every 2–3 seconds until the status is succeeded or failed.

Read the result URL from output.video.url. Download it before expires_at (30 days after storage). On failure, inspect error and credits_refunded.

Generation lifecycle →Error reference →

Build your request

280 credits / 5s video

ModeResolution

Examples only. Run on your server with your API key.

# Set FLUX1_IDEMPOTENCY_KEY once per generation; reuse it on retries.
curl --request POST 'https://flux1.ai/api/v1/generations' \
  --header "Authorization: Bearer $FLUX1_API_KEY" \
  --header 'Content-Type: application/json' \
  --header "Idempotency-Key: ${FLUX1_IDEMPOTENCY_KEY:?Set a unique key for this generation}" \
  --data '{
  "model": "seedance-2-fast",
  "prompt": "A paper boat drifting across a quiet pond, slow tracking shot",
  "resolution": "720p",
  "duration": 5,
  "aspect_ratio": "16:9",
  "generate_audio": true
}'

202 · POST /api/v1/generations

{
  "id": "gen_example",
  "status": "queued",
  "model": "seedance-2-fast",
  "media_type": "video",
  "credits": 280,
  "credits_refunded": false,
  "input": {
    "prompt": "A paper boat drifting across a quiet pond, slow tracking shot",
    "resolution": "720p",
    "duration": 5,
    "aspect_ratio": "16:9",
    "generate_audio": true
  },
  "output": null,
  "expires_at": null,
  "content_expired": false,
  "error": null,
  "created_at": "2026-09-07T08:00:00.000Z",
  "completed_at": null
}

Text, first-frame and first/last-frame modes share the displayed price. Only 480p/720p and integer durations of 4–15 seconds are supported. Generated audio is optional and does not add a separate charge. Reference video/audio inputs and automatic duration are not supported.

Resolution names are provider tiers. Actual dimensions and media duration can be rounded; output.video.duration records the requested seconds.

The final video is stored before success and expires 30 days after storage. Download it before expires_at; no email reminder is sent. Retry uncertain submissions with the same Idempotency-Key.

Provider contract: KIE Seedance 2 Fast.