Seedance 2.5 API: Native 4K Video in Seconds
Most video-generation tutorials stop at a basic text-to-video call. That leaves the interesting part — scripting a precise, multi-shot cinematic sequence with synced audio, all from one request — undocumented. Seedance 2.5 closes that gap. With first-last frame control plus advanced audio generation, you can bookend a scene exactly and let the model fill in coherent motion and dialogue end-to-end. This guide covers what the model does, the API reference on Muapi, and a working quickstart.
What Is Seedance 2.5?
Seedance 2.5 is ByteDance's latest video generation model, available through the Muapi API. It is a significant step up from both Seedance 2.1 and the 2.0 generation across the metrics developers actually care about. The headline change is native 4K resolution rendering — not upscaled output, but generation at full 4K. It also extends clip length to up to 16s clip duration, produces photorealistic quality output, and ships with advanced audio generation baked into the same call.
Where 2.0 was effectively a silent, shorter-form text-to-video engine, 2.5 turns a single request into a near-complete production step: longer, sharper, and with sound. For developers building automated video pipelines, that means fewer post-processing stages and fewer external dependencies stitched on top.
Key Features and Capabilities
Here are the capabilities that matter when you wire Seedance 2.5 into a product, each tied to a concrete use case.
- Native 4K resolution and multi-resolution output. Choose from 480p/720p/1080p/4K resolution options. Draft at 480p to validate a prompt cheaply, then re-run the locked seed at 4K for the final master.
- Six aspect ratio presets. Aspect ratios 16:9/9:16/1:1/4:3/3:4/21:9 cover every distribution surface — 16:9 for YouTube, 9:16 for TikTok and Reels, 1:1 for feed posts, and 21:9 for cinematic letterboxed trailers.
- Up to 16-second duration. Long enough to carry a full beat — an intro, an action, and a resolution — in a single clip instead of stitching fragments.
- First-last frame control. Supply a starting image and an ending image and the model interpolates a coherent motion path between them. This is the feature for precise scene bookending: lock a product's opening pose and closing hero shot, and let Seedance handle the transition.
- Advanced audio generation. Enable audio and the model scores and voices the clip. For dialogue, put the spoken line in quotes inside your prompt — that is how you drive lip-sync via dialogue in quotes. A character saying
"We launch at dawn."will have mouth movement matched to that line. - Photorealistic quality. Output holds up for realistic product, character, and environment work rather than only stylized animation.
Seedance 2.5 API Reference on Muapi
Seedance 2.5 ships as two variants:
seedance-2.5-text-to-video— generate a clip from a text prompt alone. Playgroundseedance-2.5-image-to-video— drive generation from an input image (and, with first-last frame control, an end image too). Playground
Both live under https://muapi.ai/api/v1/<variant>.
Authentication. Every request authenticates with your Muapi API key, passed in the x-api-key header. Generate or copy your key from your Muapi account dashboard; never embed it in client-side code.
Key input parameters:
| Parameter | Description |
|---|---|
prompt | Scene description. Wrap spoken dialogue in quotes for lip-sync. |
image_url | Source image (image-to-video variant). |
aspect_ratio | One of 16:9, 9:16, 1:1, 4:3, 3:4, 21:9. |
resolution | One of 480p, 720p, 1080p, 4K. |
duration | Clip length in seconds, up to 16. |
generate_audio | Boolean flag enabling advanced audio generation. |
seed | Integer seed parameter for reproducibility — same seed plus same inputs yields the same clip. |
Cost estimation. Pricing scales per second by resolution tier — lower resolutions (480p/720p) cost the least per second, with 1080p and native 4K stepping up from there. Because you pay per second, a 16-second 4K clip is your most expensive call; draft at a lower tier first and reserve 4K for finals. Check the playground pages above for current per-second rates per tier.
Quickstart Code Example
The example below submits a text-to-video request at 4K, 16 seconds, 16:9, with audio enabled and a fixed seed, then polls until the video URL is ready. It also shows the dialogue-in-quotes pattern for lip-sync. The cURL submit call is shown first, followed by the full Python flow.
# Submit (cURL)
curl -X POST https://muapi.ai/api/v1/seedance-2.5-text-to-video \
-H "x-api-key: YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"prompt": "Cinematic wide shot of a pilot in a cockpit at dawn, she turns and says \"We launch at dawn.\"",
"aspect_ratio": "16:9",
"resolution": "4K",
"duration": 16,
"generate_audio": true,
"seed": 12345
}'
import time
import requests
BASE = "https://muapi.ai/api/v1/seedance-2.5-text-to-video"
HEADERS = {"x-api-key": "YOUR_API_KEY", "Content-Type": "application/json"}
payload = {
"prompt": (
"Cinematic wide shot of a pilot in a cockpit at dawn, "
'she turns to the camera and says "We launch at dawn."'
),
"aspect_ratio": "16:9", # 16:9 / 9:16 / 1:1 / 4:3 / 3:4 / 21:9
"resolution": "4K", # 480p / 720p / 1080p / 4K
"duration": 16, # up to 16 seconds
"generate_audio": True, # advanced audio generation + lip-sync
"seed": 12345, # reproducible output
}
# 1. Submit the job
resp = requests.post(BASE, json=payload, headers=HEADERS)
resp.raise_for_status()
job_id = resp.json()["request_id"]
# 2. Poll for the result
status_url = f"https://muapi.ai/api/v1/predictions/{job_id}/result"
while True:
result = requests.get(status_url, headers=HEADERS).json()
if result.get("status") == "completed":
print("Video URL:", result["outputs"][0])
break
if result.get("status") == "failed":
raise RuntimeError(result.get("error"))
time.sleep(5)
For first-last frame control, switch to seedance-2.5-image-to-video and supply your start frame via image_url (with the end frame as that variant accepts it) to bookend the shot precisely.
Tips for Better Results and Common Pitfalls
- Reuse the seed across resolution tiers. Lock your composition with the seed parameter at 480p, then re-render the identical seed at 4K. You get the same shot at higher fidelity without re-rolling.
- Match aspect ratio to platform. Use
9:16for short-form (TikTok, Reels, Shorts),16:9for standard players, and21:9for cinematic, letterboxed sequences. Setting this up front avoids cropping and reframing in post. - Balance resolution against length. A 16-second 4K clip is the heaviest, slowest, and priciest combination. If you need length, consider 1080p; if you need maximum sharpness for a short hero shot, go 4K at a shorter duration.
- Respect the 16-second ceiling. This is the practical maximum per clip — do not expect a single call to return minutes of footage. Build longer pieces by chaining clips, using first-last frame control to keep the last frame of one clip as the first frame of the next for seamless continuity.
- Write dialogue in quotes for lip-sync. Audio and lip-sync follow the quoted text in your prompt. Keep spoken lines short and natural so mouth movement tracks cleanly.
- Validate input images for image-to-video. Confirm your
image_urlis reachable and in a standard format before submitting; a broken or unsupported source image is a common cause of failed jobs.
The single most frequent mistake is expecting unlimited-length output. Seedance 2.5 is built around tight, high-quality clips up to 16 seconds — plan your pipeline to chain them, not to demand one monolithic render.
Related
- Seedance 2.0 Mini API: Prompts, Pricing & Integration Guide — the fastest/cheapest Seedance tier for high-volume and draft workflows
- Seedance 2.1 API: Prompts, Parameters & Integration Guide — the previous generation, useful for migration context
- Seedance 2.0 vs. Kling 3.0: Which Physics Engine Actually Wins? — how Seedance compares to Kling
- The State of AI Video in 2026 — full landscape comparison including Sora, Kling, and Seedance
- Seedance Evolution: From 1.5 to 2.0 — history of the Seedance model line
- Happy Horse 1.1 API Guide — the #1-ranked Alibaba video model, a strong alternative for character-driven generation
FAQ
How do I authenticate with the Seedance 2.5 API on Muapi and where do I find my API key?
Authentication uses your Muapi API key, sent in the x-api-key request header on every call (for example, x-api-key: YOUR_API_KEY). You generate and copy the key from your Muapi account dashboard. Keep it server-side and never expose it in client-side or public code.
Does Seedance 2.5 support generating audio automatically, and how do I enable lip-sync in my prompts?
Yes. Set generate_audio to true and the model produces audio alongside the video via advanced audio generation. To drive lip-sync, write the spoken dialogue in quotes inside your prompt — for example, she says "We launch at dawn." — and the character's mouth movement is matched to that line.
What is the maximum video length and highest resolution I can request through the Seedance 2.5 API? The maximum clip duration is 16 seconds, and the highest resolution is native 4K. You can also request 480p, 720p, or 1080p. Note that combining 16 seconds with 4K is the most resource- and cost-intensive request, so draft at a lower tier and reserve 4K for final renders.
