How Long Can Seedance Videos Be? 15s Now, 30s Next

Seedance videos can be 4 to 15 seconds long per generation. That is the official range for every Seedance 2.0 tier, set in ByteDance's model documentation, at 24 frames per second with a default of 5 seconds when you do not specify^[1]. The 15-second ceiling is a hard cap, not a plan limit: no platform, subscription, or API tier extends it, which is the answer to the "why does Seedance only make 15-second videos" complaints in every language.

The more useful questions sit around that number: what duration actually costs, how productions get past 15 seconds today, whether Runway's extend feature applies (short answer: no), and what changes when Seedance 2.5's announced 30-second generation ships. All four, sourced, below.

TL;DR

• The range is 4–15 seconds per generation, 24fps, default 5s, on Seedance 2.0, Fast, and Mini alike^[1]. There is also a smart mode (duration −1) that lets the model pick a length to fit the prompt^[1].
• You pay by the second, so a 15-second clip costs exactly 3x a 5-second clip at the same tier; on reAPI that is anywhere from $0.45 (Mini, 480p, video ref) to $6.07 (Standard, 1080p, text mode) per 15s clip^[2].
• Longer stories are chained, not generated: the API returns the final frame of a clip on request, and feeding it forward as the next clip's first frame is the documented continuity mechanism^[1].
• Runway does host Seedance 2.0, but its "Extend Video" is a Gen-3 feature, unavailable for Seedance and retiring in July 2026 anyway^[3][4].
• Seedance 2.5 officially claims 30-second single-pass generation^[5], with a July release window; a 180-second beta figure circulates unverified.

How the duration setting actually behaves

Duration on Seedance 2.0 is a request parameter, an integer from 4 to 15 seconds^[1]. Three behaviors worth knowing before you script against it.

First, the default is 5 seconds, and most platform UIs inherit it, which is why "my videos are always 5 seconds" is usually just an untouched setting. Second, ByteDance documents a smart-duration mode, passing −1, where the model chooses a length appropriate to the prompt^[1]; useful for dialogue beats, risky for anything that must cut on a beat grid. Third, when reference videos are involved, the input budget is separate from output duration: up to 3 reference clips totaling 15 seconds feed in regardless of how long the output runs^[1].

Frame budget: at 24fps^[1], 15 seconds is 360 frames, and that is the arena where long-generation quality lives or dies; temporal drift compounds per frame, which is exactly why vendors cap length rather than let quality decay advertise itself.

What each extra second costs

Per-second billing makes duration a linear cost dial, and the tier matters far more than the length. On reAPI's current rates^[2], a maximum 15-second clip runs:

The practical takeaway for anyone budgeting story content: fifteen seconds of Mini costs less than five seconds of Standard at 1080p. If your cut allows mixed tiers, spend Standard on the hero shots and Mini on connective footage, and the per-minute cost of a chained sequence drops by more than half. The live pricing table has all cells current.

Going past 15 seconds today

There is exactly one sanctioned mechanism and one hosted-platform myth to clear up.

The mechanism is last-frame chaining. The API can return a generation's final frame (return_last_frame)^[1]; hand that image to the next request as its first frame, keep your reference set identical, and the seam carries composition and lighting across clips. A 60-second sequence is four chained generations plus a crossfade-free edit. The technique, along with the reference discipline that keeps characters stable across the joins, is the core of our character consistency guide.

The myth is "Seedance extend on Runway." Runway does serve Seedance 2.0, including the Fast and Mini tiers, from its Standard plan up^[3], but the Extend Video feature people remember belongs to Runway's own Gen-3 models, was never available for third-party models, and is scheduled for retirement at the end of July 2026^[4]. On Runway, continuing a Seedance clip means the video-to-video route, which is a restyle, not an extension. Chaining via last frame remains the honest way to lengthen Seedance footage anywhere.

The 30-second future, dated July

The 15-second ceiling is about to move, officially. ByteDance's promotional page for Seedance 2.5 headlines 30-second continuous single-pass generation with segment-level prompt control^[5], and Volcano Engine's documentation portal dates the release to July^[6]. A beta tester's claim of 180-second enterprise generations is a single unverified post; treat it accordingly.

Doubling the single-pass length halves the seams in narrative work, and segmented prompts aim to replace the shot-chaining workflow outright. Whether quality holds across 30 seconds is the open question no one outside the beta can answer; everything confirmed so far is collected in our Seedance 2.5 pre-launch guide.

FAQ

How long can a Seedance 2.0 video be?

4 to 15 seconds per generation, at 24fps, across all tiers; the default is 5 seconds^[1]. Longer sequences are made by chaining generations through the returned last frame.

Why are my Seedance videos only 5 seconds?

That is the default duration parameter. Set it explicitly, up to 15, or use the smart mode (−1) to let the model choose^[1].

Why does Seedance only create 15-second videos?

It is a model-level cap in ByteDance's documentation^[1], applied identically on every platform. Long single generations degrade temporal consistency, so vendors cap where quality holds; the successor raises the ceiling to a claimed 30 seconds^[5].

Does a 15-second clip cost more than a 5-second one?

Exactly 3x at the same tier; billing is per output second^[2]. Tier choice moves cost far more than duration: 15 seconds of Mini ($0.45–$0.72) undercuts 5 seconds of 1080p Standard ($2.02)^[2].

Does Runway have Seedance extend?

No. Runway hosts Seedance 2.0 for generation^[3], but Extend Video is a Gen-3-only feature that is being retired in July 2026^[4]. Lengthening Seedance footage means last-frame chaining, on any platform.

Will Seedance 2.5 make longer videos?

That is its headline claim: 30-second continuous generation, officially stated on ByteDance's own promo page, with a July release window^[5][6].

Duration is a workflow, not a setting

Fifteen seconds is the canvas, per-second billing is the meter, and last-frame chaining is how Seedance videos become as long as the story needs today. Set duration deliberately, mix tiers to protect the budget, and keep the reference set frozen across the chain. The Seedance 2.0 API on reAPI exposes the whole loop, duration, references, and last-frame return, behind one endpoint, and when Seedance 2.5 doubles the canvas this month, the same pipeline simply makes fewer joins.

References

1. Volcano Engine / BytePlus (ByteDance). Seedance 2.0 — durations, frame rate, smart duration, reference limits, return_last_frame. Retrieved July 2026 from docs.byteplus.com/en/docs/ModelArk/1520757
2. reAPI. Seedance 2.0 — model page and live pricing. Retrieved July 2026 from reapi.ai/models/seedance-2-0
3. Runway. Third-party models on Runway — Seedance 2.0 availability. Retrieved July 2026 from help.runwayml.com/hc/en-us/articles/50488490233363
4. Runway. Extend Video (Gen-3) — feature scope and retirement notice. Retrieved July 2026 from help.runwayml.com/hc/en-us/articles/30266515017875
5. Volcano Engine (ByteDance). Doubao Seedance 2.5 — official promotional page (30-second generation). Retrieved July 2026 from ark.volcengine.com/promotion?modelName=seedance-2-5
6. Volcano Engine (ByteDance). Documentation portal — Seedance 2.5 July release notice. Retrieved July 2026 from volcengine.com/docs/search?q=Seedance 2.5

Further reading

• reAPI. Seedance 2.0 Character Consistency: References, Voice, Shots. reapi.ai/blog/seedance-2-0-character-consistency-guide
• reAPI. Seedance 2.5: What We Know Before the Public Launch. reapi.ai/blog/seedance-2-5-what-we-know-2026
• reAPI. Cheapest Seedance 2.0 in 2026: Real Prices, Compared. reapi.ai/blog/cheapest-seedance-2-0-2026