Kling 4.0 Flash Video Edit API for Prompt-Driven Clip Changes

Send one 3-20 second video to POST /api/v1/videos/generations with model: kling-4-0-flash-edit and describe the change in prompt: swap an outfit, restyle the scene or regrade the colors. Up to 10 style reference images can guide the edit. The 720p output keeps the aspect ratio and the original audio of your video; track the job with the returned img_uuid.

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Color grading desk with a video frame being restyled on a monitor

Change the Clip You Already Have

Tag the source and style images

Refer to the source as <<<video_1>>> and to style images as <<<image_1>>>, <<<image_2>>> in the order of image_urls.

Read the Kling 4.0 Flash Video Edit API docs

Fabric swatches pinned beside a video monitor in a wardrobe studio

Source aspect ratio and audio are kept

There is no ratio or sound field: the edit follows the source frame and keeps the original soundtrack.

Read the Kling 4.0 Flash Video Edit API docs

Film reel next to an audio waveform display

Sources from 3 to 20 seconds

Longer videos are rejected, not trimmed. duration: "auto" (default) matches the source; an integer 3-20 sets the length.

Read the Kling 4.0 Flash Video Edit API docs

Timeline ruler and stopwatch on an editing desk

One source video is required; images are optional style guides.

Kling 4.0 Flash Video Edit Request Fields and Limits

model

Always kling-4-0-flash-edit.

prompt (required)

Editing instructions, up to 2500 characters. Use <<<video_1>>> and <<<image_N>>>.

video_urls (required)

Exactly one URL, 3 to 20 seconds. MP4 or MOV, up to 200MB, height 700-4553px.

image_urls

Optional, up to 10 style reference images. Up to 10MB each, width and height at least 300px, aspect ratio between 2:5 and 5:2.

duration and resolution

duration: "auto" (default) or an integer 3-20. resolution: 720p only.

Rejected fields

Sources over 20 seconds, ratio / aspect_ratio, sound / generate_audio, negative_prompt, seed, image_url / image_end_url / keyframes and 1080p / 4K are rejected before any tokens are charged.

custom_callback_url

Optional public HTTPS URL. GoEnhance POSTs the same body as GET /api/v1/jobs/detail when the task status changes, with up to 3 retries.

Billed on output seconds + max(source seconds, output seconds).

Kling 4.0 Flash Video Edit API Pricing

720p: 3.7143 tokens ($0.074286) per billed second

Reference images are not charged.

How billed seconds are counted

The source length is measured before charging and rounded up. With duration: "auto" you pay for twice the source length.

5-second source, auto duration

10 billed seconds: 37.14 tokens ($0.7428).

10-second source, 20-second output

40 billed seconds: 148.57 tokens ($2.9714).

Integrate the Kling 4.0 Flash Video Edit API

1. Create an API key

Generate a key at /keys and send it as Authorization: Bearer <key>.

2. Prepare the request

Put your 3-20 second source video at a public URL in video_urls, plus optional style images.

3. Store img_uuid

POST model, prompt and the assets to /api/v1/videos/generations, then poll GET /api/v1/jobs/detail with the img_uuid.

4. Save the video

When the status is success, download the edited video and store it on your side.

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Edits that keep the original performance.

What Developers Build with Kling 4.0 Flash Video Edit

Outfit and prop swaps

Change clothing or objects in a clip while keeping the motion.

Style transfer

Restyle footage as anime, clay or film looks with style images.

Color and weather changes

Turn day into night or add snow without reshooting.

UGC remix features

Let users restyle short clips in a social app with one prompt.

Common questions about requests and billing.

Kling 4.0 Flash Video Edit API FAQ

What source length is supported?

3 to 20 seconds. Longer videos are rejected, not trimmed.

Is the original audio kept?

Yes. The output keeps the audio of your video; sound / generate_audio are rejected.

Can I change the aspect ratio?

No. The output follows the source video and ratio is rejected.

Why is a 5-second edit billed for 10 seconds?

Billing is output seconds + max(source, output). With the default auto duration both are 5 seconds.

How is it different from Kling 4.0 Video Edit?

Flash is 720p only and accepts sources up to 20 seconds, at a lower per-second rate.

Start Building with the Kling 4.0 Flash Video Edit API

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