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/reference-to-video on POST /jobs/createTask, from $0.564.

Introduction

Kling 4.0 Flash reference-to-video creates a new 720p scene using a required prompt and supplied references. Add up to 10 images and up to 5 video clips with a combined duration of 20 seconds. Name images as @Image1 and videos as @Video1, continuing the numbers in upload order.

Use the prompt to explain what each reference contributes. In the desert example, one image identifies the subject while two videos guide camera movement in a dusk scene. New clips run 3–20 whole seconds with a 5-second default and include synchronized audio; keep_original_audio can retain a reference video’s sound. Reference audio files are not supported.

Key features

• Assign up to 10 reference images to subjects, objects, or scene details in the prompt.
• Guide motion and framing with up to 5 videos totaling no more than 20 seconds.
• Use @Image1 and @Video1 labels to connect the scene description to the supplied files.
• Generate a 3–20 second 720p result with audio, or retain reference video sound with keep_original_audio.
• Follow input framing with auto, or select 16:9, 9:16, 1:1, or 21:9.

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

• Place a subject from an image into a desert social scene guided by short motion clips.
• Explore a character and location combination using separately named image references.
• Build several short scene drafts around a chosen camera movement for a content review.

Prompt guide & pro tips

• Identify each image’s role, such as “@Image1 provides the subject,” before describing the new scene.
• Explain what to borrow from a video, such as “use the slow camera approach from @Video1,” so the reference has a defined purpose.
• Describe the new setting, such as “a quiet desert at dusk,” to distinguish the requested scene from the reference material.
• Keep the requested action concise, such as “the traveler stops beside the sign,” when drafting a 3-second result.
• If generating a fresh soundtrack, add a cue such as “Sound: dry wind and a distant train” to guide the included audio.

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/reference-to-video 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/reference-to-video",
  "input": {
    "prompt": "A slow aerial shot drifting over a misty pine forest at sunrise",
    "aspect_ratio": "auto",
    "duration_seconds": 5
  }
}'

# 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 · Edit 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