kling 4.0 - reapi

What is Kling 4.0 - reAPI

Kling 4.0 is Kuaishou's fourth-generation Kling video model, available on reAPI as a unified pay-as-you-go API. It generates 3–30 second clips with stereo sound at 720p or 1080p from text, keyframes, or image, video, and audio references, and can edit or extend existing videos. Announced on September 28, 2026, Kling 4.0 has been callable on reAPI since October 22, 2026.

How to use Kling 4.0 - reAPI

1. Sign up at reAPI and create an API 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.
2. Send a POST request to /api/v1/videos/generations with model kling-4-0 and the desired parameters (prompt, resolution, duration, aspect ratio, and any media references).
3. Store the returned task id and poll GET /api/v1/tasks/{id} every 1–2 seconds until the task completes.
4. Download the finished MP4 video with stereo sound.

Mode is implicit: which media fields you send decides how the request runs. For example, sending only a prompt triggers text-to-video; sending first_frame_image and/or last_frame_image triggers frames-to-video; sending image_urls, video_urls, or audio_urls triggers reference mode; setting omni_reference_task_type to edit with a video_url triggers edit mode; setting it to extend triggers extend mode.

Features of Kling 4.0 - reAPI

• Five generation modes on one endpoint: text-to-video, frames-to-video, reference-based generation, video editing, and video extension.
• Clip length: 3 to 30 seconds per generation (default 5 seconds).
• Resolution: 720p or 1080p (default 720p).
• Aspect ratios: 16:9, 9:16, 1:1, or 21:9 (auto in reference mode only).
• Audio: Stereo sound included in every output.
• Frames-to-video: Pin the first frame, the last frame, or up to 8 keyframes in between.
• Reference mode: Up to 10 images, 5 videos, and 3 audio clips (15 files total). Name them in the prompt as @Image1 or @Video1.
• Edit mode: Rewrite an existing video with a new setting, season, or look. Without a duration, the output matches the input.
• Extend mode: Continue a video from its last frame.
• Output format: MP4 video with sound.
• Pay-as-you-go: Credit-based pricing (1 credit = $0.001 USD); unused credits never expire; failed tasks are refunded automatically.
• Unified API: One model id kling-4-0 covers all modes; same API key works across all reAPI models.

Use Cases of Kling 4.0 - reAPI

• Long single takes: Generate continuous shots up to 30 seconds, such as a lighthouse keeper climbing a spiral staircase in one take.
• Reference-driven scenes: Use multiple images, videos, and audio clips to guide the generation, e.g., a paper lantern drifting down a canal with specific visual and audio references.
• Video editing: Restyle or transform existing footage—change the setting, season, or visual style while preserving the original motion.
• Video extension: Seamlessly continue a video from its last frame to create longer sequences.
• Keyframe control: Pin specific frames (first, last, or intermediate) to precisely direct motion and composition.
• Creative storytelling: Combine text prompts with audio references to generate scenes with synchronized sound, like a street food vendor flipping noodles with sizzling oil and crowd chatter.

Pricing

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

• Per output second (text, frames, reference without videos, extend):
  • 720p: $0.1425 per second
  • 1080p: $0.2125 per second
• Per billed second (edit and reference with videos; billed as output + max(output, input)):
  • 720p: $0.0850 per billed second
  • 1080p: $0.1275 per billed second

A 5-second sample at the cheapest tier costs $0.713 (713 credits). Testing budget guide: $10 ≈ 14 tests, $50 ≈ 70 tests, $100 ≈ 140 tests. No monthly subscription; pay as you go.

FAQ

What is Kling 4.0?
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.

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.

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 Kling 4.0 tier, in early access inside Kling's app since September 28, 2026. It is not on reAPI yet; the Kling 4.0 Flash page tracks its status.

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.