Seedance 2.5 API

Introduction

Seedance 2.5 Video extend continues a clip you already have. Send it as video_url with a prompt for what happens next. The platform takes the last 30 seconds of your clip at most (the whole clip, if it is shorter) and hands them to Seedance 2.5 reference-to-video as reference footage. The model generates a new segment of 4 to 30 seconds that carries the scene on, and the two are joined into one MP4: your full original first, then the continuation. The new segment also comes back as its own file, so you can keep extending or edit the pieces separately.

Key features

Continuity comes from footage, not from a single frame. Seedance reads the ending of your clip, its movement, camera direction and sound, as context, so speed and direction carry over better than when a model only sees one still. The first new frame is generated rather than copied from your last one, so describe the motion you want to continue and keep the camera language consistent.

One file back, plus the new piece on its own. The joined file keeps your clip’s frame rate and its framing, with no black bars, and is encoded as H.264 MP4 with AAC sound. To line the seam up, the picture may be trimmed or adjusted by a few percent at the edges. If the model returns a noticeably different shape, the new segment is scaled to fill your frame and centered, cropping what spills over. Sound from your source stays, sound generated for the new segment follows it with a short fade at the seam, and a silent side is padded with silence. The second asset in the output is the new segment alone.

Everything else is Seedance 2.5 reference-to-video. A source shorter than 2 seconds is too short to continue from and is turned down.

Request parameters

Pricing

Prices are in credits, the same credits you use on the website (1 credit = $0.01). The hold is taken when the task is accepted and settled to the actual charge when it finishes; failed tasks are refunded.

Each task is rounded up to whole credits, so one run at the lowest tier costs 56 credits for a 5-second clip ($0.56).

For an exact number before you run, send the same body to POST /jobs/quote.

Use cases

Lengthen a shot that ended too early: a dance that stops mid-move, a tracking shot that cuts before the subject reaches the door, a product spin that stops before the label faces the camera. Extend it and describe the remaining action.

Build a longer sequence step by step. Generate a first shot, extend it, then extend the joined result again. Sources are limited to 60 seconds, so for a long chain extend the latest segment rather than the whole joined clip.

Prompt guide & pro tips

Describe the next beat, not the whole scene. The reference already shows who and where, so spend the prompt on the action that follows, the camera move and the sound. Repeat the camera language your clip ended on, such as a slow push-in or a handheld follow, so the seam reads as one take.

End your source where you want to continue. Seedance leans on the closing seconds of the reference; a clip that ends mid-cut, on a fade or on a different shot pulls the continuation the wrong way. Trim first. Sources of 2 to 60 seconds are accepted as MP4, MOV or WebM.

Keep the resolution consistent. Resolution only sets the quality of the new segment, so a 480p segment after a 1080p source looks softer than the original.

API quick start

Call the Seedance 2.5 API in three steps

1. Create an API key. Sign in to PopNow and create a key in the API console. Keys start with sk-popnow- and use the same credits as the website.
2. Send the request. POST /jobs/createTask with model bytedance/seedance-2.5/video-extend and an input object that follows the parameter table. The response returns a task ID straight away.
3. Get the result. Poll GET /jobs/recordInfo with the task ID, or pass a callBackUrl and we post the result to it. Download the output links when the task succeeds.

# 1. Create the task. Keep the Idempotency-Key if you retry after a network error.
export IDEMPOTENCY_KEY="$(uuidgen)"
curl -X POST https://api.popnow.ai/api/v1/jobs/createTask \
  -H "Authorization: Bearer $POPNOW_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $IDEMPOTENCY_KEY" \
  -d '{
  "model": "bytedance/seedance-2.5/video-extend",
  "input": {
    "prompt": "A slow aerial shot drifting over a misty pine forest at sunrise",
    "video_url": "https://media.popnow.ai/effects/flower-bloom-1abd6efb.mp4",
    "resolution": "720p",
    "duration_seconds": 5,
    "generate_audio": true
  }
}'

# 2. Copy data.taskId from the response, then poll until state is succeeded, failed, canceled or expired.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.popnow.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
  -H "Authorization: Bearer $POPNOW_API_KEY"

Replace the prompt and any links with your own. The API tab has the response, polling and callback reference.

Seedance 2.5 API questions

All Seedance models

Seedance 2.0 reaches 4K but stops at 15 seconds, and costs less per second. Seedance 2.5 runs up to 30 seconds per take and takes the largest reference sets.

• Seedance 2.5 APIByteDance's newest: 30-second clips with native audioFrom 56 credits for a 5-second clip
• Seedance 2.0 Mini APILightweight Seedance for quick 720p drafts with soundFrom 9 credits for a 5-second clip
• Seedance 2.0 APICinematic clips up to 4K with native audioFrom 33 credits for a 5-second clip
• Seedance 2.0 Fast APIFaster Seedance 2.0 with sound at 720pFrom 17 credits for a 5-second clip
• Seedance 1.5 Pro APINative-audio clips with an optional locked cameraFrom 9 credits for a 5-second clip

Other video APIs

• MiniMax H3 APIExpressive clips with audio, up to 2KFrom 28 credits for a 5-second clip
• Kling 3.0 API4K clips, multi-shot cuts and motion controlFrom 51 credits for a 5-second clip
• Vidu Q4 Preview APIUp to 4K clips with sound and spoken dialogueFrom 34 credits for a 5-second clip
• Wan 3.0 APIUp to 30-second clips with synced audioFrom 34 credits for a 5-second clip
• Kling O3 APIKling’s unified model: create, animate, reference and edit up to 4KFrom 51 credits for a 5-second clip
• MiniMax H3 Max APIFast clips with ambience, effects and musicFrom 38 credits for a 5-second clip

More about Seedance 2.5

Try it

Seedance 2.5 AI Video Generator onlineCreate videos with Seedance 2.5 in PopNow

Compare

Kling 3.0 vs Seedance 2.5Seedance 2.5 vs Wan 3.0Seedance 2.0 vs Seedance 2.5

Docs

Seedance 2.5 model ID and input schema in the API docsPopNow API quickstart: your first request in five minutesImage to video guide for the PopNow APIWebhooks: get Seedance 2.5 results without polling