Kling 4.0 API

About Kling 4.0

Up to 30-second 1080p clips with keyframes; may queue when busy.

Call it with the model name kling/4.0/image-to-video on POST /jobs/createTask, from 162 credits for a 5-second clip ($1.62).

Introduction

Kling 4.0 Image to video animates your opening frame into a clip of 3 to 30 seconds at 720p or 1080p. Add a closing frame to pin where it ends, and up to 8 in-between frames, in order, to direct the path between the two. The prompt is optional; every clip comes back with a stereo soundtrack.

Choose a Kling 4.0 mode by starting material

Key features

First frame, in-between frames, last frame

image_url sets the opening, last_image_url the ending and keyframe_image_urls the beats in between, in the order they should appear. In our test an astronomer at a telescope (opening), bending to the eyepiece (in-between) and leaning on the railing with her arms crossed (closing) came back as one continuous 3-second move through all three poses.

The shape follows your frame

Leave aspect_ratio on auto and the clip keeps the opening frame's shape; pick 16:9, 9:16, 1:1 or 21:9 to override it.

Sound comes with it

Every clip carries a two-channel soundtrack. Describe the sound in the prompt to steer it.

Request parameters

Pricing

Prices are in credits, the same credits you use on the website (1 credit = $0.01). The hold is taken when the task is accepted and settled to the actual charge when it finishes; failed tasks are refunded.

For an exact number before you run, send the same body to POST /jobs/quote.

Use cases

Bring a still to life

A portrait, a product shot or a frame from an earlier clip - describe only what happens next and the look, wardrobe and setting come from your image.

Storyboard to motion

Draw or generate the key poses of a shot, upload them as opening, in-between and closing frames, and the model fills the motion between them.

Continue a scene

Take the last frame of a previous clip as the opening frame of the next one to keep a character and a set consistent across shots.

Prompt guide & pro tips

Keep your frames consistent

Opening, in-between and closing frames should share the same character, wardrobe, set and camera position. Frames that disagree force a cut or a morph.

Describe the motion, not the picture

The image already shows what everything looks like. Spend the prompt on the action, the camera move and the sound.

Fewer, clearer keyframes

Each in-between frame is a point the clip must pass through. For a short clip one or two are enough; too many in a few seconds make the motion rushed.

API quick start

Call the Kling 4.0 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- and use the same credits as the website.
2. Send the request. POST /jobs/createTask with model kling/4.0/image-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/image-to-video",
  "input": {
    "prompt": "A slow aerial shot drifting over a misty pine forest at sunrise",
    "image_url": "https://media.popnow.ai/influencer/examples/marco.webp",
    "aspect_ratio": "auto",
    "resolution": "720p",
    "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 API questions

More about Kling 4.0

Try it

Kling 4.0 AI Video Generator onlineCreate videos with Kling 4.0 in PopNow

Endpoints

Kling 4.0 · Create VideoKling 4.0 · Reference to Video

Docs

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