Kling 4.0 Flash API

About Kling 4.0 Flash

Kling 4.0 Flash is the lighter member of Kuaishou's Kling 4.0 generation, made for drafts, social clips and quick iteration. It renders 720p video from 3 to 20 seconds, always with generated sound. Animate an opening image, build a shot from up to 10 image and 5 video references, or edit an existing clip while its scene and motion stay in place.

Call it with the model name kling/4.0-flash/video-edit on POST /jobs/createTask, from $0.1512.

Introduction

Kling 4.0 Flash video-edit starts from an existing clip and a required instruction about what to change. Supply a source of 3–20 seconds and, if useful, up to 10 reference images. The 720p result keeps the source’s scene, subject, motion, and camera move while applying the described edit.

Output duration follows the source, and sources longer than 20 seconds are cut at that point. In our tests, the observatory wardrobe edit kept a 5.04-second source at 5.04 seconds. Source sound is retained by default; set keep_original_audio to false for newly generated synchronized audio.

Key features

• Build a visual revision around an existing performance and camera move.
• Add up to 10 reference images when the edit calls for a particular visual reference.
• Keep source timing in the output, with source material capped at 20 seconds.
• Retain the original soundtrack by default or generate fresh synchronized audio.
• Receive 720p output in auto framing or one of four supported aspect ratios.

Request parameters

Pricing

Prices are in USD. The API uses a separate USD balance. Website credits cannot be used or transferred to it, and API funds cannot be transferred to website credits. When a task is accepted, we reserve the maximum quoted amount from your API balance. On completion, we charge for actual usage, never more than the hold, and release the remainder. If the task fails, the hold is released.

Send the same request body to POST /jobs/quote to see the estimated and maximum USD charge before running. A quote does not run the task or charge your balance.

Use cases

• Try an emerald evening gown in an observatory clip while keeping the action.
• Review different coat colors across versions of a short social scene.
• Prepare visual draft variations of a recorded movement with the source soundtrack retained.

Prompt guide & pro tips

• Start with what to preserve, such as “retain the scene and camera movement,” to define the edit’s fixed elements.
• Name a focused change, such as “make the coat charcoal gray,” before requesting several variations.
• Assign a role to each added image, such as “use the jacket shown in @Image1,” so the reference relates to the change.
• Describe material and color together, such as “an emerald velvet gown,” when the wardrobe is the subject of the edit.
• For a fresh soundtrack, turn off keep_original_audio and include a cue such as “Sound: a low motor hum and evening wind.”

API quick start

Call the Kling 4.0 Flash API in three steps

1. Create an API key. Sign in to PopNow and create a key in the API console. Keys start with sk-popnow-. API calls use your separate USD balance.
2. Send the request. POST /jobs/createTask with model kling/4.0-flash/video-edit and an input object that follows the parameter table. The response returns a task ID straight away.
3. Get the result. Poll GET /jobs/recordInfo with the task ID, or pass a callBackUrl and we post the result to it. Download the output links when the task succeeds.

# 1. Create the task. Keep the Idempotency-Key if you retry after a network error.
export IDEMPOTENCY_KEY="$(uuidgen)"
curl -X POST https://api.popnow.ai/api/v1/jobs/createTask \
  -H "Authorization: Bearer $POPNOW_API_KEY" \
  -H "Content-Type: application/json" \
  -H "Idempotency-Key: $IDEMPOTENCY_KEY" \
  -d '{
  "model": "kling/4.0-flash/video-edit",
  "input": {
    "prompt": "A slow aerial shot drifting over a misty pine forest at sunrise",
    "video_url": "https://media.popnow.ai/effects/flower-bloom-1abd6efb.mp4",
    "aspect_ratio": "auto"
  }
}'

# 2. Copy data.taskId from the response, then poll until state is succeeded, failed, canceled or expired.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.popnow.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
  -H "Authorization: Bearer $POPNOW_API_KEY"

Replace the prompt and any links with your own. The API tab has the response, polling and callback reference.

Kling 4.0 Flash API questions

More about Kling 4.0 Flash

Try it

Kling 4.0 Flash Image to Video AI onlineCreate videos with Kling 4.0 Flash in PopNow

Endpoints

Kling 4.0 Flash · Image to VideoKling 4.0 Flash · Reference to Video

Docs

Kling 4.0 Flash model ID and input schema in the API docsPopNow API quickstart: send your first requestImage to video guide for the PopNow APIWebhooks: get Kling 4.0 Flash results without polling