Introduction
Wan 2.5 Video Extend continues a clip you already have. Send it as video_url and, if you like, a prompt for what happens next. The final frame of your clip becomes the opening frame of a new Wan 2.5 image-to-video shot of 5 or 10 seconds, and the two are joined into one MP4: your original first, then the continuation, with the repeated seam frame removed. The new segment also comes back as its own file, so you can keep extending or edit the pieces separately.
Key features & highlights
Continuity comes from the last frame. Wardrobe, set, light and where everyone stands carry over because the new segment literally starts on your final frame. Motion does not carry over the same way: the model sees one still, not the whole clip, so describe the movement you want to continue instead of assuming it will keep its speed or direction.
One file back, plus the new piece on its own. The joined MP4 keeps your clip’s frame rate and its framing, with no black bars. 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. It is encoded as H.264 MP4 with AAC sound. Sound from your source stays; sound for the new segment follows it; a silent side is padded with silence so picture and sound stay in step at the seam. The second asset in the output is the new segment alone, ready for another extend or for an editor.
Bring your own sound for the new part. Pass audio_url and the new segment is built against that track, so a spoken line or a beat lands where you expect. It shapes only the new segment: your original keeps the sound it had, and the two are joined as they are.
Everything else is Wan 2.5 image-to-video. The new segment runs on the same routes, with the same content range and the same per-second price as the image-to-video endpoint, and a failed generation is refunded the same way. If the generation succeeds but the join itself cannot be built, the task fails and the charge is refunded.
Request parameters
| Parameter | Required | Description |
|---|---|---|
prompt | No | Optional. What happens next: the action that follows, the camera move and a line about sound. at most 1500 characters |
negative_prompt | No | What must not appear in the new segment: a second person, captions, a prop the last frame keeps bringing back. Up to 500 characters. at most 500 characters |
video_url | Yes | The clip to continue: MP4, MOV or WebM, up to 60 seconds. Its final frame becomes the opening frame of the new segment, so cut it on a clean, sharp frame. at least 1 characters |
resolution | No | Resolution the new segment is generated at: 480p, 720p or 1080p, default 720p. Match your source’s resolution so the seam shows no step in sharpness. |
duration_seconds | No | Length of the new segment: exactly 5 or 10 seconds, default 5. Your source is added on top and is not billed. |
audio_url | No | Audio for the new segment: a voice line or music cue it should follow, so speech and beats land where you expect. WAV or MP3, 3 to 30 seconds and up to 15 MB. at least 1 characters |
enable_prompt_expansion | No | Off by default. Turn it on for a one-line idea; leave it off when the prompt is already a precise action. Default: |
seed | No | 0 to 2147483647. Fix it when comparing resolution or length from the same clip; for a random draw, leave the field out rather than sending 0. |
Pricing
Billed per second of the new segment at the resolution you choose; the source clip you send is not billed.
| Specification | Price |
|---|---|
| $0.045 / second |
| $0.09 / second |
| $0.135 / second |
Use cases
Lengthen a shot that ended too early: a product turntable that stops before the label faces camera, or a walk that cuts before the subject reaches the door. Extend it by a few seconds and describe only the remaining motion.
Build a longer sequence step by step. Generate a first shot, extend it, then extend the joined result again; each step bills only the seconds it adds. Because every step starts from a single frame, watch each seam before stacking the next one.
Prompt guide & pro tips
Describe the next beat, not the whole scene. The frame already fixes who and where, so spend the prompt on the action that follows, the camera move and the sound. Repeat the camera language your clip ended on, such as a slow push in or a locked shot, so the seam reads as one take. The prompt is optional, but one clear action line gives steadier motion than none.
Trim before you extend. The last frame is the only picture the model sees, so a blurred, mid-cut or heavily compressed ending carries straight into the continuation. Cut your source on a clean, sharp frame first. Sources of up to 60 seconds are accepted as MP4, MOV or WebM.
Match the resolution to your source. resolution only sets how sharp the new segment is generated. Set it to your source's resolution and set duration_seconds to the length you actually need: the charge follows the new segment only.
API quick start
# Generate the idempotency key once; reuse it when retrying after a lost response.
export SPICY_IDEMPOTENCY_KEY="${SPICY_IDEMPOTENCY_KEY:-$(uuidgen)}"
curl -X POST https://api.spicyapi.ai/api/v1/jobs/createTask \
-H "Authorization: Bearer $SPICY_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: $SPICY_IDEMPOTENCY_KEY" \
-d '{
"model": "alibaba/wan-2.5/video-extend",
"input": {
"duration_seconds": 5,
"resolution": "720p",
"video_url": "https://example.com/reference.mp4"
}
}'
# Copy data.taskId from the response into TASK_ID, then poll the status.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.spicyapi.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
-H "Authorization: Bearer $SPICY_API_KEY"
See the API reference for authentication, the complete schema, polling, and error handling.
