When was Kling 4.0 released?

Kling announced Kling 4.0 in a release note on September 28, 2026, with the faster Kling 4.0 Flash in early access the same day. Kling 4.0 has been callable on reAPI since October 22, 2026.

Is Kling 4.0 available through an API?

Yes. On reAPI, send a POST to /api/v1/videos/generations with model kling-4-0 and poll the returned task for the video. The API reference lists every field, mode, and limit.

Is Kling 4.0 free or paid?

Kling 4.0 is paid per second of video at $1 = 1,000 credits. New reAPI accounts get a small test credit, but one Kling 4.0 clip costs more than it covers, so top up before your first generation. Failed tasks are refunded automatically. See the pricing table on this page for the current per-second rates.

Does Kling 4.0 require a monthly subscription?

No. reAPI is pay as you go: you buy credits, each Kling 4.0 task deducts its cost, and unused credits never expire. There is no monthly plan to keep.

How do I get a Kling 4.0 API key?

Sign up at reAPI and create a key under Settings, API keys. The same key works for Kling 4.0 and every other model on reAPI; send it as a Bearer token.

How long can a Kling 4.0 video be?

Each Kling 4.0 generation runs 3 to 30 seconds; the default is 5. In extend mode the duration is the length of the new part, and the result includes the original video.

What resolutions does Kling 4.0 support?

720p and 1080p on reAPI, in 16:9, 9:16, 1:1, or 21:9. Kling's own spec sheet also lists 4K and 10-bit HDR; reAPI does not offer those for Kling 4.0.

How is a Kling 4.0 edit billed?

Edits, and reference requests that include videos, bill at the video-input rate for output seconds plus the longer of the output and the input. The input is the total length of the input videos, rounded up and capped at 30 seconds. Every other mode bills output seconds at the standard rate.

What's new in Kling 4.0 vs Kling 3.0?

Kling 4.0 doubles the clip length to 30 seconds, adds keyframes, takes image, video, and audio references, and can edit or extend a video. Kling 3.0 still offers multi-shot prompts and 4K, so pick it when you need those.

What is Kling 4.0 Flash?

Kling 4.0 Flash is the faster, lower-cost Kling 4.0 tier: 3–20 second 720p clips with sound from text, reference images, reference videos, and elements. It opened in early access inside Kling's app on September 28, 2026, and has been callable on reAPI since November 6, 2026 as kling-4-0-flash.

Can I use my own video with Kling 4.0?

Yes. Set omni_reference_task_type to edit and pass a video of at least 3 seconds to restyle it, or set it to extend to continue it from the last frame. Media inputs are public HTTP(S) URLs.

Kling 4.0 — Kuaishou's Next-Gen AI Video Model

Kling 4.0 is Kuaishou's newest Kling video model, live on reAPI. Kling 4.0 generates 3–30 second clips with stereo sound from a prompt, keyframes, or image, video, and audio references, and it can edit and extend a video you already have, at 720p or 1080p.

Highlights: 3–30 s · 720p / 1080p · stereo sound
Best for: Long single takes, reference-driven scenes, video edits
Input: Text, frames, or image, video, and audio references
Output: MP4 video with sound

Input

Prompt*

Required except for frame-only image to video

Resolution

720p or 1080p · default 720p

Duration

3–30 seconds · default 5

Aspect ratio

16:9 / 9:16 / 1:1 / 21:9 · auto in reference mode only

Estimated cost~$0.749749 credits

Result

Try one of these prompts

Pricing

Credit-based — 1 credit = $0.001 USD. Pay only for completed generations.

First test cost

$0.749749 credits

One 5-second sample at the cheapest tier.

Testing budget guide

Add credits

$10

≈ 13 tests

$50

≈ 66 tests

$100

≈ 133 tests

Category	720p	1080p
Per output second · text, frames, reference without videos, extend	$0.1496 Price · 1 second	$0.2231 Price · 1 second
Per billed second · edit and reference with videos (output + max(output, input))	$0.0892 Price · 1 billed second	$0.1339 Price · 1 billed second

What is Kling 4.0?

Kling 4.0 is the fourth generation of Kuaishou's Kling video model, announced on September 28, 2026. On reAPI, Kling 4.0 is one model id, kling-4-0, that covers five jobs: text to video, image to video with up to 10 frames, reference-based generation from images, videos, and audio, video editing, and video extension. Every Kling 4.0 clip runs 3 to 30 seconds at 720p or 1080p and comes back as an MP4 with stereo sound. You send one Kling 4.0 request, keep the task id, and download the finished video when the task completes.

Kling 4.0 long single-take video generation

5 generation modes on one endpoint

Mode is implicit: which media fields you send decides how the request runs.

Text to video

prompt

A prompt alone. Kling 4.0 writes the shot, the motion, and the sound.

Frames to video

first_frame_image + last_frame_image | image_with_roles

Pin the first frame, the last frame, or up to 8 keyframes in between, and Kling 4.0 fills the motion.

Reference

image_urls | video_urls | audio_urls

Up to 10 images, 5 videos, and 3 audio clips, 15 files in all. Name them in the prompt as @Image1 or @Video1 and Kling 4.0 follows them.

Edit

omni_reference_task_type: edit + video_url

Rewrite an existing video with Kling 4.0: a new setting, a new season, a new look. Without a duration, the output matches the input.

Extend

omni_reference_task_type: extend + video_url

Continue a video from its last frame with Kling 4.0. You get the original plus the new part, and can set where it ends.

What you can build with this model

Real-world workflows and production use cases you can build and ship with this model.

One 30-second take

Kling 4.0 generates up to 30 seconds in one clip, twice the 15-second cap of Kling 3.0. Its creator says this Kling 4.0 walk through a Japanese neighborhood came from a single text-to-video request, with no stitching.

Characters that talk

Kling 4.0 generates sound with every clip, and more accurate lip sync is one of the upgrades Kling lists for it. Its creator made this 15-second Kling 4.0 scene of three soldiers trading lines on a tidal flat, straight to camera.

Stylized action, start to finish

A paper samurai duels a cream warrior on a city built from cake, then folds itself into an origami bird. Kling 4.0 holds one material look through fast cuts, so a stylized Kling 4.0 short reads as one piece.

Why reAPI for Kling 4.0

Five jobs, one model id

Kling 4.0 generates, animates frames, follows references, edits, and extends under one id, kling-4-0. The mode follows the media you send, so your code keeps one request shape.

One key for every model

The same reAPI key runs Kling 4.0, Kling 3.0, Seedance, Veo, and the rest of the catalog on /api/v1/videos/generations. No new vendor account.

Pay per second, no subscription

Kling 4.0 bills by the second at the rate for its resolution. Credits never expire, and failed tasks are refunded automatically.

Kling 4.0 vs Kling 3.0

Both models are live on reAPI on the same endpoint. Kling 4.0 adds longer clips, keyframes, references, editing, and extension; Kling 3.0 keeps multi-shot prompts and 4K.

Capability

Kling 4.0 on reAPI

Kling 3.0 on reAPI

Clip length

3–30 s

3–15 s

Resolution

720p or 1080p

720p, 1080p, or 4K

Frame control

First and last frames, up to 8 keyframes

First frame plus optional last frame

References

Up to 10 images, 5 videos, 3 audio clips

Up to 3 Elements, 2–4 images each

Edit and extend

Both, on an existing video

Not available

Sound

Always on, stereo

Optional native audio

Kling 4.0 and Kling 3.0 values reflect each model's parameters on reAPI on October 22, 2026.

Call Kling 4.0 in three steps

step 01
Create an API key
Sign up and create a key in the dashboard. New accounts get a small test credit; add credits before your first Kling 4.0 clip, which costs more than that.
Open
step 02
Try Kling 4.0 in the playground
Pick a mode, add your media, and generate. Copy the request from the API tab when you like the result.
Open
step 03
Send the request
POST to /api/v1/videos/generations with model kling-4-0, then poll the Kling 4.0 task until it completes and download the video.
Open

docs/api/kling-4-0

API reference

Drop-in code and the full parameter table.

View full reference

curl -X POST https://reapi.ai/api/v1/videos/generations \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "kling-4-0",
    "prompt": "A lighthouse keeper climbs a spiral staircase at dawn, one continuous take from the first step to the lamp room.",
    "resolution": "720p",
    "duration": 5,
    "aspect_ratio": "16:9"
  }'

Parameter validation failed

Rejected synchronously with the failing field named. Check enum values, ranges, and URL fields — nothing is charged.

Authentication or balance issue

401 means a missing or invalid Bearer key; 402 means the reserve exceeds your balance. Manage keys and credits in the console.

Content or material rejected

Reference material and outputs pass automated moderation. Rejected tasks fail with a clear error and a full refund.

Task failed or timed out

A task that reaches a failed state is never charged — the reserve refunds automatically. Keep the task id and retry when ready.

Frequently asked questions

Common questions about this model.

Kling 4.0 is Kuaishou's fourth-generation Kling video model, following Kling 3.0. On reAPI it generates 3–30 second clips with stereo sound at 720p or 1080p from text, keyframes, or image, video, and audio references, and it can edit or extend an existing video.