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

Introduction

Kling 4.0 Flash image-to-video builds a 720p clip from one opening image. Upload a JPEG, PNG, or WebP file and optionally describe how the scene should move. Set 3–20 whole seconds for the result, or use the 5-second duration default.

This is a practical starting point for exploring movement in an existing portrait or scene still. The sample uses a WebP portrait, a smile, and shifting sunset light. Flash accepts an opening frame without closing-frame or intermediate-keyframe controls, and every result includes sound.

Key features

• Begin from one opening image in JPEG, PNG, or WebP format; WebP worked in our tests.
• Add an optional motion prompt to direct the action after the supplied still.
• Use auto aspect ratio to follow the image, or select 16:9, 9:16, 1:1, or 21:9.
• Draft 3–20 seconds at a fixed 720p resolution with a 5-second default.
• Describe ambience or music for the generated synchronized soundtrack.

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

• Animate a portrait for a social post with a smile and a small lighting change.
• Turn a landscape still into a short concept with drifting clouds and outdoor ambience.
• Review several camera directions from the same opening image for a content batch.

Prompt guide & pro tips

• Describe what follows the still, such as “clouds drift over the ridge,” to give the opening image a next event.
• Start with a restrained action, such as “the subject smiles slowly,” before testing a more involved sequence.
• Add a specific camera instruction, such as “gentle push toward the window,” so the motion brief includes framing.
• State how light should change, such as “warm sunset light crosses the room,” when lighting is part of the idea.
• Give the soundtrack a clear setting, such as “Sound: distant traffic and evening wind,” to direct the audio that comes with the clip.

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/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-flash/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",
    "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 price on other platforms

Options	PopNow	fal
720p	$0.1128/ s	$0.0940/ s

Each platform's public API list price for the same model and settings, checked Nov 6, 2026.

Kling 4.0 Flash API questions

All Kling models

Choose Kling 4.0 Flash for fast 720p drafts and edits up to 20 seconds. Move to Kling 4.0 when you need 1080p, clips up to 30 seconds, closing or intermediate keyframes, or audio references.

• Kling 4.0 APIUp to 30-second 1080p clips with keyframes, edits and extensions; may queue when busyFrom $0.564 for a 5-second clip
• Kling O3 APIKling’s unified model: create, animate, reference and edit up to 4KFrom $0.336 for a 5-second clip
• Kling 4.0 Flash APIFast 720p Kling clips with sound, 3 to 20 secondsFrom $0.564 for a 5-second clip
• Kling 3.0 Turbo APIFaster Kling 3.0 with sound on every clipFrom $0.56 for a 5-second clip
• Kling 3.0 API4K clips, multi-shot cuts and motion controlFrom $0.336 for a 5-second clip
• Kling Avatar 2.0 APIA portrait that speaks or sings your audio, up to 5 minutesFrom $0.0512 per second
• Kling 2.6 API1080p clips with optional sound and motion controlFrom $0.345 for a 5-second clip
• Kling 2.5 Turbo API1080p clips with a soundtrack on every takeFrom $0.28 for a 5-second clip
• Kling 2.1 Master APISilent 1080p clips with fine prompt controlFrom $1.08 for a 5-second clip
• Kling 2.1 APIAnimate a frame at 720p or 1080p, with an optional end frameFrom $0.175 for a 5-second clip

Other video APIs

• MiniMax H3 APIExpressive clips with audio, up to 30 seconds or 2KFrom $0.125 for a 5-second clip
• MiniMax H3 X API2–15-second videos with sound, up to 1080pFrom $0.11 for a 5-second clip
• Seedance 2.5 APIByteDance's newest: 30-second clips with native audioFrom $0.369 for a 5-second clip
• Vidu Q4 Preview APIUp to 4K clips with sound and spoken dialogueFrom $0.225 for a 5-second clip

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 · Reference 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