Version

ByteDance Seedance 2.5

Seedance 2.5 generates up to 30 seconds of continuous video with sound in one pass, and takes up to 50 reference files: 30 images, 10 videos, 10 audio clips. In exchange its resolution ceiling is 720p, half of what the previous model in the same family delivered.

  • 30 seconds in one pass
  • 50 reference inputs
  • 720p ceiling

current

Last checked: This is a reference page. It is re-checked against the vendor sources and updated when a new version ships. What changed

The number the product page leaves out

ByteDance own Seedance 2.5 page talks about 30-second generation and precise reference control, and says nothing about resolution. The answer sits in their API documentation: for this model the resolution parameter accepts exactly two values, 480p and 720p, and defaults to 720p. The same page lists four values up to 4k for Seedance 2.0. So in that one column, the newer model is behind its own predecessor.

We confirmed it in a second, independent place. Runway OpenAPI schema, for the same model resold on their API, spells it out in the ratio parameter: Seedance 2.5 supports 480p and 720p only. Two sources, one number.

What 30 seconds means exactly

The duration parameter accepts 4 to 30 seconds for this model, and Volcano Engine own guide says the ceiling moved from the 15 seconds of the 2.0 series to 30, with the option to extend twice after that. It is the longest single-pass clip among the four models in our table, and the gap is not small: Veo 3.1 stops at eight seconds.

In real work, single-pass length is the thing that removes the edit. Three ten-second clips stitched together carry three chances of a face or a light shifting between them. One 30-second clip carries none.

Fifty reference inputs, and how they are counted

The official guide breaks the ceiling down: 30 images plus 10 videos plus 10 audio files, 50 in total. Audio alone is enough as a reference and does not have to arrive alongside an image. For anyone who needs one consistent character or one consistent product across several scenes, that number matters more than the resolution does.

Editing, which gets mentioned less

The same model edits an existing video: swapping the subject, adding or removing an object, even stripping the background music. The documentation writes down the constraints, and writes them down badly: the input video has to be 4 to 30 seconds, the aspect ratio must stay adaptive, and duration must be -1. Miss any of the three and the error does not come back when you submit the task, it comes back after processing has started. Anyone who has not read that page first pays with time and credits to learn it.

Specifications

Model ID doubao-seedance-2-5-260628 Source
Input text, image, video, audio Source
Output video, audio Source
Available on Volcano Engine Ark API, Runway API Source
Longest clip in one pass 30 seconds Source
Resolution ceiling 720p Source
Vertical resolution 720 lines of vertical resolution Source
Native audio yes Source
Reference inputs 50 reference inputs Source

Using it from Iran

We check this ourselves from an Iranian connection, because no vendor documents it and every listicle guesses.

Reachable
not checked
Payment
not checked
Free tier
no
Measured on

How we checked: ByteDance publishes no supported-countries list for this model. The official route to buy it is the Volcano Engine console in China, which requires at least 200 RMB of balance before the model can be enabled, and the second route is the same model resold on US platforms that sit under US export control law. We have neither tested the network from inside Iran nor found a document saying an Iranian can or cannot open an account, so this column reads as unknown rather than open.

What it is good at

  • Thirty seconds of continuous video in a single generation, the longest in our table today
  • Up to fifty reference inputs across three types: image, video and audio
  • Audio is on by default and generated with the picture rather than in a second pass
  • Edits and extends an existing video with the same model, no side tool needed

Where it falls short

  • The resolution ceiling is 720p. That is not enough for a large screen or an advertising delivery, and Seedance 2.0 went to 4K in the same column.
  • The official route to buy it is the Chinese Volcano Engine console, which wants at least 200 RMB of balance first.
  • The constraints on an edit task are strict and the error arrives after processing starts, not on submission.
  • We have read no document about access from Iran, so this model Iran column reads as unknown and scores nothing in the table.
  • ByteDance publishes no generation time, so we do not know how long those 30 seconds take to arrive.

Our take

If your work is narrative and you need a character to hold, this model has something the others do not today: 30 seconds and 50 references. If the output has to end up on a billboard or a television, stop here and take Kling instead. No upscale turns 720p into 4K.

Questions people actually ask

How long a video can Seedance 2.5 generate

Up to 30 seconds in one pass, and the duration parameter accepts 4 to 30 seconds. Volcano Engine own guide says you can then extend it twice.

Does Seedance 2.5 output 4K

No. The API documentation allows only 480p and 720p for this model. The 4K option lives on Seedance 2.0, not on 2.5.

Can Seedance 2.5 be bought from Iran

We do not know, and we will not guess. ByteDance publishes no country list and we have run no test from inside Iran. We sell no accounts and recommend no circumvention.

Sources

  1. ByteDance Seed, Seedance 2.5 model page vendor source 12 August 2026
  2. Volcano Engine Ark, create video generation task API vendor source 12 August 2026
  3. Volcano Engine Ark, Doubao Seedance 2.5 guide vendor source 12 August 2026
  4. Runway API pricing, per second of output vendor source 12 August 2026