From "coming soon" to live

Kling announced Kling 4.0 on September 28, 2026, opened Flash to Ultra subscribers the same day and made the full model available to everyone on October 15. At the time, Kling listed developer API access as coming soon, so our Kling 4.0 release article and the Kling 4.0 page said the same. API access is now open, and both models are connected behind the VideoGenAPI endpoint.

Kling 4.0 vs Kling 4.0 Flash on VideoGenAPI

Kling 4.0 FlashKling 4.0
Model keykling-4-flashkling-4
Clip length3 to 20 seconds3 to 30 seconds
Resolution720p720p or 1080p
Text-to-video formats16:9, 9:16, 1:1, 21:916:9, 9:16, 1:1, 21:9
AudioStereo, always onStereo, always on
Image-to-videoStart frameStart frame, optional end frame
Price$0.15 per second$0.25/s at 720p, $0.35/s at 1080p
Use it forDrafts, iteration, social clipsFinal renders, longer shots

In image-to-video mode, the output follows the proportions of your start frame, so aspect_ratio only applies to text-to-video.

How to call it

curl -X POST "https://videogenapi.com/api/v1/generate" \
  -H "Authorization: Bearer $VIDEOGEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "kling-4",
    "prompt": "A dancer in a red dress crosses a rain-soaked plaza at night, spins under a street lamp and looks into the camera, steady tracking shot",
    "duration": 15,
    "resolution": "1080p",
    "aspect_ratio": "21:9"
  }'

Use "model": "kling-4-flash" for a fast 720p draft of the same prompt. For image-to-video, add "image_url", and with Kling 4.0 an optional "end_image_url". The response returns a generation_id: poll GET /api/v1/status/{id} until the status is completed, then read video_url. More in the generate reference.

Pricing

  • Kling 4.0 Flash: $0.15 per second, so a 10-second clip costs $1.50.
  • Kling 4.0 at 720p: $0.25 per second, so a 10-second clip costs $2.50.
  • Kling 4.0 at 1080p: $0.35 per second, so a 30-second clip costs $10.50.

The amount is checked against your balance before the job starts and debited when it is accepted. Failed generations are refunded automatically. A practical workflow: iterate with Flash, then render the keeper with Kling 4.0 by changing only the model field.

Kling 3 stays in your plan

Kling 3 remains included in every monthly plan, with no per-second charge, for clips up to 10 seconds. Choose Kling 4.0 when you need length beyond 10 seconds, 1080p with an end frame, or 21:9 framing. For long shots with native sound, Wan 3.0 also goes up to 30 seconds.

Frequently asked questions

How do I use the Kling 4.0 API?
Send POST /api/v1/generate to VideoGenAPI with "model": "kling-4" (or "kling-4-flash"), a prompt and a duration. Kling 4.0 accepts 3 to 30 seconds at 720p or 1080p; Flash accepts 3 to 20 seconds at 720p. Add "image_url" for image-to-video.
How much does Kling 4.0 cost on VideoGenAPI?
Kling 4.0 costs $0.25 per second at 720p and $0.35 at 1080p; Kling 4.0 Flash costs $0.15 per second. It is debited from your balance and refunded if the generation fails.
What is the difference between Kling 4.0 and Kling 4.0 Flash?
Flash is the fast tier: 720p only, 3 to 20 seconds, no end frame, about a minute to render a 5-second clip. Kling 4.0 adds 1080p, clips up to 30 seconds and an optional end frame.
Does Kling 4.0 generate audio?
Yes. Both Kling 4.0 and Kling 4.0 Flash return two-channel stereo audio generated with the video. Audio is always included; there is no silent option.
Is Kling 3 still available?
Yes. Kling 3 remains on VideoGenAPI and is included in every monthly plan, for clips up to 10 seconds.

Sources

Third-party facts and prices were checked on the date of publication and can change; check the provider before buying.

  1. fal: Kling 4.0 text-to-video
  2. fal: Kling 4.0 image-to-video
  3. fal: Kling 4.0 Flash text-to-video
  4. fal: Kling 4.0 Flash image-to-video