
BLACKFORESTLABS FLUX 3 First & Last Frame-to-Video API by Black Forest Labs
Generate a video between a start frame and an end frame using FLUX 3.
BLACKFORESTLABS FLUX 3 First & Last Frame-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 First & Last Frame to Video
FLUX 3 First & Last Frame to Video generates a smooth video transition between two images. Provide a start frame and an end frame, add a prompt describing the motion in between, and the model fills in a cinematic clip that begins and ends exactly on your images — with optional native audio.
Why Choose This?
-
Precise start and end control Pin both the opening and closing frames for exact transitions.
-
Native audio generation Produce video and synchronized audio in a single request.
-
Explicit duration required Duration must be set explicitly so the model knows where to place the end frame.
-
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 |
|---|---|---|
| start_image_url | Yes | URL of the image used as the first frame (PNG, JPEG, or WebP) |
| end_image_url | Yes | URL of the image used as the last frame (PNG, JPEG, or WebP) |
| prompt | No | Text description of the motion between the two frames |
| 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 — an explicit value is required to place the end frame |
| 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 |
How to Use
- Provide your start image — the video opens on this frame.
- Provide your end image — the video closes on this frame.
- Write your prompt — describe the motion, action, and camera movement between the two frames.
- Set duration explicitly — pick a value from 5–20 seconds (
autois not supported here). - 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
- Scene Transitions — Morph smoothly from one scene to another.
- Before & After — Animate a transformation between two states.
- Storytelling — Bridge two key moments in a visual narrative.
- Product Demos — Show a product moving from one configuration to another.
Pro Tips
- Keep the two images' aspect ratios similar for the cleanest interpolation.
- Describe what happens between the frames in the prompt, not what's in them.
- Use longer durations for complex transitions; shorter for snappy cuts.
- Describe ambient sounds for richer audio output when
generate_audio: true.
Notes
- Both
start_image_urlandend_image_urlare required. durationcannot be"auto"— the model needs an explicit frame count to anchor the end image.- Accepted image formats: PNG, JPEG, WebP.
- 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 Keyframes to Video — Pin multiple images to exact frame positions.
- FLUX 3 Extend Video — Continue an existing video clip.


















