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Kling 4.0 Flash Keyframe to Video API: Image-to-Video

Animate a first-frame image into a Kling 4.0 Flash video. 3-20s clips at 720p with native audio. Pay per generation, no subscription. Kling 4.0 Flash Keyframe-to-Video animates a first-frame image into a 3-20 second 720p clip, with the frame addressable in the prompt as @firstframe.

Interactive model controls

Kling 4.0 Flash Keyframe-to-Video animates a first-frame image into a 3-20 second 720p clip, with the frame addressable in the prompt as @first_frame.

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Overview

About this model

Kling 4.0 Flash Keyframe-to-Video animates a first-frame image into a 3-20 second 720p clip with native audio. Mention the frame in your prompt with @first_frame and describe how the scene moves; the output follows the image's aspect ratio. If you leave the frame out, the request behaves as plain text-to-video. Flash accepts a first frame only: middle keyframes and a last frame are not supported. For multi-frame sequences, 1080p and 30-second clips use Kling 4.0 Keyframe to Video; for characters and references use Kling 4.0 Flash Reference to Video.

1Image-to-video: Bring a product shot, portrait or illustration to life.
2Social: Animate a still into a quick vertical clip for Reels and Shorts.
3Previews: Test a motion idea on a single frame before a high-quality render.
4Ads: Turn a key visual into a short moving shot with native sound.
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Pricing & Value

Cost analysis

muapiapp$0.094 per second ($0.47 per 5s clip)

$0.094/s of output video at 720p.

** Competitor pricing is estimated based on similar model architectures and usage tiers.

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Technical Details

Configuration schema

Promptstring

Video description (max 8000 chars). Mention the first frame with @first_frame.

Default ValueAnimate @first_frame as one continuous shot: the camera slowly pushes in as the skier turns her head toward the sunlit window, gentle cabin sway, ambient wind
First Frame URLstring

First-frame image URL. Mention as @first_frame.

Default Value-
Durationint

Video length in seconds (3-20).

Default Value5
ResolutionEnum (1 options)

Output resolution (Kling 4.0 Flash is 720p only).

Default Value720p
Aspect RatioEnum (4 options)

Only used when no first frame is provided (plain text-to-video); otherwise the output follows the first frame.

Default Value-
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Implementation Guide

Developer documentation

How to Use Kling 4.0 Flash Keyframe to Video

  1. Provide the first frame: Set first_frame_url to a publicly accessible image.

  2. Mention the frame in the prompt: Use @first_frame and describe the motion, camera and sound.

  3. Configure output: duration (3-20s). Output is always 720p and follows the image's aspect ratio; aspect_ratio only applies when no frame is supplied.

  4. Submit and collect the result: poll /api/v1/predictions/{request_id}/result or pass a webhook_url.

curl -X POST https://api.muapi.ai/api/v1/kling-4.0-flash-keyframe-to-video \
  -H "Content-Type: application/json" \
  -H "x-api-key: YOUR_API_KEY" \
  -d '{"prompt": "Animate @first_frame as one continuous shot: the camera slowly pushes in as she turns toward the window", "first_frame_url": "https://example.com/first.png", "duration": 10}'
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Common Questions

Frequently asked

What are the duration and resolution limits?

3 to 20 seconds per clip at 720p only.

Can I add middle keyframes or a last frame?

No. Flash accepts a first frame only. Use Kling 4.0 Keyframe to Video for middle keyframes and a last frame.

What aspect ratio will the output have?

When a first frame is provided, the output follows the image's aspect ratio. aspect_ratio (16:9, 9:16, 1:1, 21:9) only applies without a frame.

How is pricing calculated?

$0.094 per second of output video, so a 5-second clip costs $0.47.

Does it generate audio?

Yes, native audio is generated with the video.

How do I get the result?

The endpoint is asynchronous. Poll /api/v1/predictions/{request_id}/result or pass a webhook_url to be notified when the video is ready.