FLUX 3 Video Length: The 20-Second Limit and How to Go Longer
Timeline concept marked at twenty seconds for a single AI video generation
FLUX 3 Video can generate up to 20 seconds with native audio in one pass. That number shows up in every capability list for a reason: it is the hard ceiling for a single generation. Longer stories are a chaining problem, not a slider problem.
Note: On TheFluxTrain, FLUX 3 duration is 5–20 seconds (Auto bills as 20 seconds). Extend continues a clip; the video editor is for assembly.
Quick answer: FLUX 3 can create up to 20 seconds of video with audio in one generation. Multi-shot or minute-long pieces need connected clips, references, and continuation. Generate on TheFluxTrain from the FLUX 3 model page, then cut in the editor.
Related: video with audio · image-to-video · release guide
Why 20 seconds is the planning unit
Write shots that fit inside one pass:
- Product hero loops
- Dialogue beats
- Transition bridges
- Social cuts that stay under twenty seconds anyway
If a beat needs 35 seconds, split it before you prompt. Two coherent clips beat one overstretched generation.
When I ran a student animation company, we lived on shot lists for the same reason. You do not ask one take to carry a whole scene if the tool (or the schedule) cannot hold it. Generative video has the same constraint, just with credits instead of render farms.
BFL's early comparisons used 10-second clips. That is evaluation length, not the product maximum.
How do you make longer videos?
Announced tools for length beyond one pass:
- Connected clips / multi-shot sequences: generate several clips, then assemble
- Visual references: carry character or style across scenes
- Continuation from existing video and audio: extend a take instead of restarting from text
- Keyframe transitions: control the joins between moments
Think like an editor: shot list first, generations second, timeline last.
Example shot list (45-second ad)
| Shot | Target length | Mode |
|---|---|---|
| 1 | 6s | Image-to-video from product still |
| 2 | 8s | Text-to-video, same references |
| 3 | 7s | Continuation from shot 2 end |
| 4 | 5s | Keyframe title card transition |
| Assemble | ~26s | NLE or TheFluxTrain video editor |
Stay honest about overlap and handles when you cut.
What breaks when you ignore the limit?
- Motion drift near the end of long asks
- Identity melt across unplanned minutes
- Audio that starts strong and wanders
- Credit burn on regenerations
Shorter clips with clear references are cheaper to fix.
Does FLUX 3 replace a timeline editor?
No. Generative continuation is not the same as cutting A-roll. You will still trim, rearrange, and mix. On TheFluxTrain, generate clips then assemble in the video editor. Status: model page.
Practical rules
- Default to 4–10 seconds for dialogue (5 seconds is the FLUX 3 minimum on TheFluxTrain)
- Reserve longer spans for simple camera moves
- Lock references before chaining
- Name files by shot so continuation inputs stay obvious
- Read video-to-video before you rely on continuation
Frequently asked questions
How long can a FLUX 3 video be?
Up to 20 seconds with audio in one pass.
Can I generate a full minute in one go?
Not according to the announced one-pass limit. Chain clips instead.
Do chained clips keep the same character?
References are meant to help. Consistency is not guaranteed across long sequences.
Did BFL test 20-second clips in its comparisons?
Published early comparisons used 10-second, 720p text-to-video with audio.
Is longer video coming later?
BFL has not published a higher one-pass duration. Roadmap items focus more on access routes and editing APIs than on a new max length.
Will TheFluxTrain raise the limit?
Not past the model max. One generation is 20 seconds. Extend and the editor handle longer pieces.
Should social ads stay under 20 seconds anyway?
Often yes. Many placements prefer short cuts. The limit matches that shape better than it matches a short film.