How to Use ByteDance Seedance 2.5: 30-Second Clips, Credit Costs and Prompting

ByteDance Seedance 2.5 is the long-form model in VdoBloom’s Seedance family: it generates a single clip of any whole-second length from 4 to 30 seconds at 480p, 720p or 1080p (10-bit colour), from a text prompt, a starting image, or both, and it costs 11.2 credits per second at 480p, 25.2 at 720p and 63.2 at 1080p. That per-second ladder is the whole story of the model — every planning decision below comes back to it.

What Seedance 2.5 is actually best at

Most video models on VdoBloom stop somewhere between 5 and 15 seconds. Seedance 2.5 runs to 30 in one generation, and that changes what you can make. A 24-second product walkthrough, a full spoken-length talking segment, a slow architectural push across a room, a dance take that does not cut in the middle of the chorus — these are shots you would otherwise have to stitch from two or three clips, fighting continuity drift at every join. One generation means one lighting state, one wardrobe, one face.

The second thing it does well is framing. Six aspect ratios are available — 16:9, 4:3, 1:1, 3:4, 9:16 and the 21:9 cinema-wide frame — so a 9:16 vertical cut and a 21:9 trailer beat come from the same model rather than from a crop. The 1080p tier was added with 10-bit colour, which matters if the clip is going into a graded edit rather than straight to a social upload.

Real specs and exact credit costs

Durations are selectable one second at a time across the entire 4-to-30-second range. There is no “pick 5, 10 or 15” restriction here, which means a 13-second insert is generated at 13 seconds instead of trimmed out of a 15-second render you paid for. At 1 credit = $0.05 (the Lite plan rate of $15 for 300 credits), here is what the tiers actually cost:

Duration	480p	720p	1080p (10-bit)
5 seconds	56 credits — $2.80	126 credits — $6.30	316 credits — $15.80
10 seconds	112 credits — $5.60	252 credits — $12.60	632 credits — $31.60
15 seconds	168 credits — $8.40	378 credits — $18.90	948 credits — $47.40
20 seconds	224 credits — $11.20	504 credits — $25.20	1,264 credits — $63.20
30 seconds	336 credits — $16.80	756 credits — $37.80	1,896 credits — $94.80
Per second	11.2 credits	25.2 credits	63.2 credits

One rate you will not find on a spec sheet elsewhere: when you supply a reference video, Seedance 2.5 is billed at a lower unit price — 6.8 credits per second at 480p, 15.2 at 720p and 38 at 1080p. The catch is that this lower rate is billed on input plus output seconds: a 10-second run from a 5-second reference is 102, 228 or 570 credits instead of 112, 252 or 632, so VdoBloom measures the reference clip you upload and adds its length to the estimate before you generate. A short reference is cheaper than a long one, and the cost shown on the button is the cost you pay.

A starting image is not a reference video. Image-to-video runs are billed at the plain rate in the table above.

How to prompt Seedance 2.5 well

Long durations punish vague prompts more than short ones do. A 4-second clip can survive an under-specified prompt because the model only has to hold an idea for four seconds; a 26-second clip will wander, repeat, or reset if you have not told it what happens over time.

Write the shot as a sequence, not as a description. Something like: “Woman in a red linen dress walks from the doorway into the kitchen, pauses at the counter, turns toward the window as morning light hits her face; camera tracks left then settles.” That prompt has three beats and a camera instruction, which is roughly the right density for 10 seconds. For 20 to 30 seconds, plan four to six beats. Name the subject once and then refer back to it consistently, rather than re-describing it — re-describing mid-prompt is a common cause of the subject changing halfway through.

Keep lens and lighting language at the start (“shallow depth of field, overcast daylight, handheld”) and motion language in the middle. Avoid stacking contradictory camera moves; one dominant move per clip reads as intentional, three reads as a glitch.

If you are working from a still, the Seedance tooling accepts a first frame, a last frame, additional reference images and reference audio, so you can pin both ends of a movement instead of hoping the model lands where you want. If your starting image is a photograph of a real person, you must have that person’s consent before animating it. Browse our Seedance prompt library if you want working prompts to adapt rather than starting from an empty box.

A worked example

Say you need a 22-second vertical clip for a skincare brand: a model applying serum, turning to camera, soft morning light.

Draft it at 480p, 9:16, 22 seconds — 247 credits, $12.35. That is not cheap, so do the beat-structure work first at a shorter length: run the same prompt at 8 seconds, 480p (90 credits, $4.50) two or three times until the subject, wardrobe and light are right. Only then extend the prompt to the full beat list and run 22 seconds at 480p to check that the motion holds across the whole duration. Finish at 720p (555 credits, $27.75) or 1080p (1,391 credits, $69.55) once. Total for a careful session: roughly 250 credits of drafting plus one finish, instead of burning 1080p renders on prompt experiments.

When to pick a different model

Seedance 2.5 is the wrong default for anything under about 8 seconds where you plan to iterate a lot. Its per-second rate is the highest in the family, and the family has cheaper members built for exactly that job:

• Seedance 2 Fast — 4 to 15 seconds, 480p or 720p, well under half the 2.5 rate at 720p. The drafting model.
• Seedance 2 Mini — the cheapest way to run twenty variations of an idea before you commit.
• Seedance 2 — the only member of the family with a 4K tier and the one to use when a hero shot will be viewed large.

Switch away from Seedance entirely when you need something the family does not offer — the /models directory lists what each of the other families is for. And if what you want is a preset motion applied to a photo rather than a written shot, the Seedance effects tab runs the same family through ready-made templates.

Getting started

Open text-to-video or the image-to-video tab, pick Seedance 2.5 in the model picker, set resolution, aspect ratio and duration, and the exact credit cost appears before you generate. New accounts start with 10 free credits and no card, which is enough to try the cheaper members of the family but not a full 2.5 run — see pricing for plans from $15 a month and credit packs from $10.39 that never expire. Paid plans download watermark-free with commercial rights.

Frequently asked questions

What is the longest video Seedance 2.5 can generate?

Thirty seconds in a single generation, selectable at any whole second from 4 upward. That is the longest single-clip duration in the Seedance family, where the other members cap at 15 seconds.

How much does a 10-second Seedance 2.5 video cost?

112 credits at 480p, 252 at 720p and 632 at 1080p — $5.60, $12.60 and $31.60 respectively at the Lite plan rate of $0.05 per credit. With a reference video supplied, the reference clip’s seconds are billed too, at the lower rate: from a 5-second reference the same 10 seconds is 102, 228 or 570 credits. Editing jobs run on that same tier — the Genjutsu AI video tool uses Seedance 2.5’s editing mode, where the source clip sets the length and aspect ratio.

Does Seedance 2.5 support 4K?

No. Its top tier is 1080p with 10-bit colour. Only Seedance 2 in this family offers a 4K tier, at 4 to 15 seconds.

Can Seedance 2.5 start from a photo?

Yes. It runs on both the text-to-video and image-to-video tabs, and it accepts a first frame, a last frame and additional reference images. Image-to-video runs are billed at the standard per-second rate, not the lower reference-video rate.

Which aspect ratios can Seedance 2.5 generate?

Six: 16:9, 4:3, 1:1, 3:4, 9:16 and 21:9. All six are available at every resolution and every duration in the 4-to-30-second range.