FLUX 3 vs Seedance 2.5: Keyframes, Duration, and Cost

Choose FLUX 3 for ordered multi-keyframe control, video-and-audio continuation, FHD output, or a Draft-to-final loop. Choose Seedance 2.5 when a 21–30-second take, a large reference pack, or prompt-driven editing removes work. Both generate sound, but their useful difference is what they let you control before generation.^[1][2]

FLUX 3 vs Seedance 2.5 at a glance

The models overlap on text/image video with sound. They separate when the brief becomes a timeline-control problem or a reference-and-editing problem.

FLUX 3 pins moments; Seedance carries a larger brief

FLUX 3 accepts up to ten images in timeline order. One is the opening frame, two are opening and closing, and additional images become evenly spaced middle keyframes.^[1]

That is the cleaner API for an approved sequence of product states or a graphic transformation where the middle matters.

Seedance 2.5 accepts up to 30 images, 10 videos, and 10 audio files. Its references can describe characters, locations, motion, sounds, and style together, but the API is not the same ordered ten-keyframe timeline.^[2]

If the instruction is “hit these five exact visual states in order,” test FLUX 3 first. If it is “make this character perform in this room using this movement and soundtrack,” Seedance's larger multimodal set is better shaped for the request.

Seedance's extra ten seconds can remove a visible edit

FLUX 3 stops at 20 seconds; Seedance reaches 30. A 26-second UGC read or continuous camera move needs at least two FLUX 3 generations but can fit in one Seedance request.

Long output is not free control. If second 27 fails, the Seedance take may need a full rerun. A planned cut at 15 seconds can make two shorter clips easier to review and replace. Use 30 seconds when continuity is the requirement, not because a larger maximum looks better on a specification table.

Editing and continuation solve different problems

FLUX 3 continuation starts from an existing clip and carries its video and audio forward. It is priced in a separate, higher continuation tier.^[1]

Seedance 2.5 classifies source-video requests as reference, edit, or extend based on the payload and prompt. It can replace or remove elements and preserve the source length in its edit path, or generate beyond a reference in an extend workflow.^[2]

Use FLUX 3 when the exact last state and soundtrack should continue. Use Seedance when the source itself needs to be changed or the request depends on several kinds of reference media.

Cost depends on the job shape

Current public reAPI rates checked August 23, 2026:

FLUX 3 is cheaper for the base examples above, and its Draft tier is an inexpensive rejection pass. A successful Draft then incurs the normal final render, so a ten-second Draft plus HD final costs $2.13 rather than $1.57.^[3]

Continuation and reference-video jobs need their own calculation. FLUX 3 continuation is $0.378/s at HD and $0.488/s at FHD. Seedance 2.5 uses discounted per-second reference rates but can bill source duration and a minimum clock. Do not carry the base table into a source-video estimate.^[3][4]

Resolution favors FLUX 3; duration favors Seedance

FLUX 3 offers FHD. Seedance 2.5 currently stops at 720P on reAPI. If the file must be delivered above 720P without a separate upscale step, FLUX 3 has the relevant tier.

Seedance's 480P tier is useful for cheap prompt checks, while FLUX 3 uses its Draft mode for the same production stage. They are not equivalent outputs: one is a lower resolution normal generation, the other is explicitly a low-quality preview meant to be finalized.

Audio claims still need a real test

Both advertise synchronized generated audio and multilingual dialogue. FLUX 3 can continue an existing soundtrack; Seedance accepts multiple audio references. Those are API facts, not proof that either will pronounce a specific Japanese name, preserve a singing voice, or sync a difficult line better.

For dialogue, use the same five utterances, character image, shot duration, and acceptance rubric. Score words missed, lip timing, voice consistency, background sound, and retry count. A viral clip is a prompt example, not a benchmark.

Which one should enter the queue first?

• FLUX 3: multiple ordered keyframes, FHD deliverable, video/audio continuation, or many disposable Drafts.
• Seedance 2.5: a 21–30-second take, large mixed-reference pack, source-video editing, or 30-second extension.
• Both: dialogue, product identity, typography, and any subjective quality question.

Two briefs that make the choice concrete

Consider a ten-second app animation with five approved UI states. The timing of each state is the work: blank screen, search, results, selected item, confirmation. FLUX 3's ordered image array maps directly to that sequence. Seedance can accept the images as references, but its larger reference capacity does not improve the timeline contract.

Now consider a 26-second character scene driven by a room image, wardrobe views, an action clip, and two sound references. FLUX 3 cannot fit the duration in one generation, while Seedance can carry the larger mixed pack and attempt the scene as one take. The risk moves to late-shot failure, but the input and duration requirements point clearly to Seedance.

Writing these two sentences before routing is often enough: “Which moments must happen when?” and “Which external assets must the model understand?” The first answer favors keyframes; the second favors multimodal reference capacity.

The live request surfaces are on FLUX 3 and Seedance 2.5. For a broader model router, see the AI video API comparison.

References

1. Black Forest Labs, “FLUX 3 Video”, August 4, 2026.
2. ByteDance Seed, “Introducing Seedance 2.5”, July 31, 2026.
3. reAPI FLUX 3 API documentation and live pricing, accessed August 23, 2026.
4. reAPI Seedance 2.5 API documentation and billing rules, accessed August 23, 2026.