How to Use ByteDance Seedance 2 Fast: Credit Costs and the Draft-Then-Finish Workflow

ByteDance Seedance 2 Fast is the drafting model of the Seedance family on VdoBloom: it keeps the flagship’s full 4-to-15-second single-second duration ladder and all six aspect ratios including 21:9, caps resolution at 480p or 720p, and costs 4.8 credits per second at 480p and 10 credits per second at 720p — a 5-second 720p clip is 50 credits, or $2.50. You use it to find out whether a prompt is worth a bigger render, and then you re-render the winner somewhere else.

What Fast trades away, and what it keeps

The temptation with a “fast” variant is to assume it is a weaker model. That is not quite what is going on here. Seedance 2 Fast keeps the parts of the flagship that govern composition and gives up the part that governs delivery.

Kept: duration selectable at every whole second from 4 to 15, so a 7-second beat is generated at 7 seconds. Kept: all six aspect ratios — 16:9, 4:3, 1:1, 3:4, 9:16 and 21:9. Kept: both text-to-video and image-to-video, plus the family’s first-frame, last-frame, reference-image and reference-video inputs. Kept: the same MODERATE content filtering as the rest of the Seedance 2 generation, so a prompt that passes on Fast passes on the flagship.

Given up: 1080p and 4K. Fast stops at 720p. That is the entire trade, and it is why a composition proven on Fast transfers without re-work — what you framed at 480p in 21:9 is what you get at 4K in 21:9 on Seedance 2.

Exact credit costs

Fast is currently carrying a limited-time discount in the model picker, so these are cheaper than the family’s usual rates. At the Lite plan rate of 1 credit = $0.05 ($15 for 300 credits):

Duration	480p	720p	480p with reference video	720p with reference video
4 seconds	19 credits — $0.95	40 credits — $2.00	11 credits — $0.55	24 credits — $1.20
5 seconds	24 credits — $1.20	50 credits — $2.50	14 credits — $0.70	30 credits — $1.50
8 seconds	38 credits — $1.90	80 credits — $4.00	22 credits — $1.10	48 credits — $2.40
10 seconds	48 credits — $2.40	100 credits — $5.00	28 credits — $1.40	60 credits — $3.00
15 seconds	72 credits — $3.60	150 credits — $7.50	42 credits — $2.10	90 credits — $4.50

The two right-hand columns apply only when you supply a reference video. A starting image does not qualify — image-to-video is billed at the plain 480p and 720p rates. Whatever your settings, the exact number is shown on the generate button before you spend anything.

For scale: the same 5-second clip at 720p is 82 credits ($4.10) on the Seedance 2 flagship, 17 credits ($0.85) on Seedance 2 Mini, and 100 credits ($5.00) on Seedance 2.5. Fast sits deliberately in the middle.

How to prompt for a drafting model

The mistake people make with Fast is writing one careful prompt and running it once. That wastes the model. Fast exists so you can run a prompt five ways cheaply — five 480p, 5-second variations is 120 credits, $6.00 — and read the results as a batch.

Vary one axis at a time. Keep the subject and setting fixed and change only the camera (“slow dolly in” / “static lockoff” / “handheld orbit left”), or keep the camera fixed and change only the light (“hard midday sun” / “overcast soft” / “golden hour backlight”). Five variations that differ in three ways each tell you nothing about which change helped.

Write in this order: subject and wardrobe, then setting, then light, then camera move, then any timing beat. Around 40 to 60 words is the useful band for a 5-second clip; a 15-second clip can carry three or four beats. Name the subject once and refer back to it rather than re-describing it mid-prompt, which is a common cause of the subject changing halfway through.

Draft at the aspect ratio you will actually deliver in. A 9:16 composition is not a cropped 16:9 one, and testing in the wrong frame invalidates the test. If you are animating a photograph of a real person, you must have that person’s consent before generating.

A worked example

A coffee brand needs a 9:16 hero loop: hands lifting a cup from a wooden counter, steam catching a window light.

Stage one, exploration — six prompt variants at 480p, 4 seconds, 9:16. That is 6 × 19 = 114 credits, $5.70. Two will be usable; four will show you what the model is misreading in your wording.

Stage two, refinement — take the winning prompt to 720p, 6 seconds, for a real look at motion quality: 60 credits, $3.00. Run it twice if the first take has a hand artifact. Roughly 120 credits, $6.00.

Stage three, delivery — if 720p is your delivery format (and for a social loop that gets re-compressed, it usually is), you are done at about 234 credits total, $11.70. If the clip is going on a landing page at full width, move the same prompt and the same 9:16 framing to Seedance 2 at 1080p, 6 seconds — 243 credits, $12.15 — for one finishing render.

When to pick a different model

Pick Seedance 2 Mini when volume matters more than quality: at 480p it is the cheapest way to run twenty ideas, and its 4-second 480p run costs less than Fast’s. Pick Seedance 2 when the output is final and will be viewed large — it is the only family member with 1080p and 4K, and 4K at 5 seconds is 414 credits ($20.70). Pick Seedance 2.5 when the shot needs to run longer than 15 seconds; it goes to 30 seconds in a single generation, which Fast cannot do at any price.

And if you want a preset motion applied to an existing photo rather than a shot written from scratch, the Seedance effects tab runs this same family through ready-made templates.

Where to run it

Seedance 2 Fast appears in the model picker on both text-to-video and the image-to-video tab. Choose resolution, aspect ratio and duration, and the credit cost updates before you generate. New accounts get 10 free credits with no card — not quite enough for a Fast run, but enough to try Mini and see how the family behaves. Plans start at $15 a month for 300 credits, one-time packs start at $2.49 for 75 credits that never expire, and paid plans download watermark-free with commercial rights.

Frequently asked questions

What is the difference between Seedance 2 Fast and Seedance 2?

Duration options (4–15 seconds in one-second steps) and all six aspect ratios are identical. Fast caps at 720p; the flagship adds 1080p and 4K. Fast returns results quicker and costs roughly half as much at 720p — 50 credits versus 82 for a 5-second clip.

How much does a 10-second Seedance 2 Fast video cost?

48 credits at 480p and 100 credits at 720p — $2.40 and $5.00 at the Lite plan rate of $0.05 per credit. With a reference video supplied, the same 10 seconds is 28 or 60 credits.

Can Seedance 2 Fast output 1080p?

No. It offers 480p and 720p only. For 1080p or 4K you need Seedance 2, and for 1080p at longer durations you need Seedance 2.5.

Do prompts written for Fast work on the other Seedance models?

Yes, and that is the intended workflow. Duration options, aspect ratios and content filtering match across Seedance 2, Fast and Mini, so a composition proven at 480p re-renders at a higher resolution without changing the prompt or the frame.

Does Seedance 2 Fast support 21:9?

Yes. All six ratios — 16:9, 4:3, 1:1, 3:4, 9:16 and 21:9 — are available at both resolutions and across the whole 4-to-15-second range, which is why it works as a cinema-wide drafting tool.