
BLACKFORESTLABS FLUX 3 Keyframes-to-Video API by Black Forest Labs
Generate a video that hits the supplied keyframe images at exact frame positions using FLUX 3.
BLACKFORESTLABS FLUX 3 Keyframes-to-Video は Black Forest Labs が開発したモデルです。Atlas Cloud(運営:Atlas Cloud AI LLC)は本モデルへのアクセスを提供するものであり、その所有者ではありません。すべての商標は各所有者に帰属します。
FLUX 3 Keyframes to Video
FLUX 3 Keyframes to Video generates a video that hits your supplied images at exact frame positions. Provide up to 10 keyframe images each pinned to a specific frame index, add a prompt describing the overall motion, and the model interpolates a cinematic clip that passes through every keyframe precisely — with optional native audio.
Why Choose This?
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Frame-accurate image placement Pin up to 10 images to any frame position in the output video (24 fps).
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Full creative control Combine multiple visual anchors with a single guiding prompt.
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Native audio generation Produce video and synchronized audio in a single request.
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Explicit duration required Duration must be set explicitly to validate keyframe positions.
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Flexible aspect ratios
auto,21:9,2:1,16:9,4:3,1:1,3:4, or9:16. -
High resolution output Generate videos in 720p or 1080p.
Parameters
| Parameter | Required | Description |
|---|---|---|
| keyframes | Yes | Array of keyframe objects (up to 10). Each must have a unique frame_index. See schema below |
| prompt | No | Text description of the overall motion and scene |
| aspect_ratio | No | Aspect ratio of the generated video. Default: auto. Options: auto, 21:9, 2:1, 16:9, 4:3, 1:1, 3:4, 9:16 |
| resolution | No | Video resolution. Default: 720p. Options: 720p, 1080p |
| duration | No | Duration in seconds. Default: 5. Options: 5–20. Cannot be auto — required to validate keyframe positions |
| generate_audio | No | Whether to generate audio. Default: true |
| safety_tolerance | No | Safety level 0 (strictest) to 4 (most permissive). Default: 2 |
| seed | No | Random seed for reproducibility |
Keyframe Object
| Field | Required | Description |
|---|---|---|
| image_url | Yes | URL of the keyframe image (PNG, JPEG, or WebP) |
| frame_index | Yes | Frame position in the video. At 24 fps, max value is duration × 24. Must be unique across all keyframes |
Frame Index Reference (24 fps)
| Duration | Max frame_index | Common anchor points |
|---|---|---|
| 5s | 120 | 0 (start), 60 (mid), 120 (end) |
| 10s | 240 | 0, 120, 240 |
| 20s | 480 | 0, 240, 480 |
How to Use
- Decide your keyframes — choose which images to anchor and at which timestamps.
- Convert timestamps to frame indices — multiply seconds by 24 (e.g. 2.5s → frame 60).
- Write your prompt — describe the overall motion and scene across the full clip.
- Set duration explicitly — pick a value from 5–20 seconds.
- Choose resolution and aspect ratio.
- Run — submit and download your video.
Pricing
Billed per second of generated video, by resolution:
| Resolution | Cost per second |
|---|---|
| 1080p | $0.319 |
| 720p | $0.187 |
Best Use Cases
- Multi-scene Stories — String together multiple shots with consistent visual anchors.
- Choreographed Motion — Sync visual beats to specific moments in the clip.
- Complex Transitions — Chain more than two images with fine temporal control.
- Storyboarding — Animate a sequence of storyboard panels into a full clip.
Pro Tips
- Always pin
frame_index: 0to the first keyframe for a clean opening. - Keep all
frame_indexvalues unique — duplicates are rejected. frame_indexcannot exceedduration × 24— validate before submitting.- Keep keyframe images visually coherent in style and lighting for smoother interpolation.
Notes
keyframesis the only required field (minimum 1 keyframe).- Up to 10 keyframes per request; each
frame_indexmust be unique. durationcannot be"auto"— an explicit value is needed to validate frame positions.- Video is generated at 24 fps.
- Generation is asynchronous — submit, then poll for the finished video.
Related Models
- FLUX 3 Text-to-Video — Generate video from a text prompt alone.
- FLUX 3 Image-to-Video — Animate a single starting image.
- FLUX 3 First & Last Frame to Video — Interpolate between exactly two images.
- FLUX 3 Extend Video — Continue an existing video clip.


















