# Kling 4.0 Flash API

> The fast, low-cost Kling 4.0: 3 to 20 seconds at 720p, always with sound, from text, a first frame, or up to 10 reference images. By Kuaishou, on Revana $0.10 per second of video.

- Model id: `kling-4.0-flash`
- Kind: video
- Maker: Kuaishou
- Tasks: Text to video, Image to video, Reference to video
- Resolutions: 720p
- Durations: 3 to 20 seconds
- Aspect ratios: 16:9, 9:16, 1:1, 21:9
- Audio: supported (`"audio": true`)
- Input images: up to 10
- Routes: 2 (starts on the cheapest, falls back automatically)
- Status: live on the API
- Page: https://revana.si/models/kling-4.0-flash

## Price (per second of video, USD)

| Resolution | Price | Credits |
|---|---|---|
| 720p | $0.10 | 10 |

100 credits = $1. Charged once, only for the route that succeeds; failed generations cost nothing.

## Request

POST https://api.revana.si/v1/generations with `Authorization: Bearer $REVANA_API_KEY` and an `Idempotency-Key` header: one key per request, made once and sent again on every resend after a timeout, a 429 or a 5xx, so the request is never made or charged twice. After a generation has failed, use a new key.

```json
{
  "model": "kling-4.0-flash",
  "input": {
    "prompt": "A slow dolly shot through a neon-lit night market in the rain, steam rising from food stalls",
    "resolution": "720p",
    "duration": 3,
    "aspect_ratio": "16:9",
    "audio": true
  },
  "max_cost_usd": 0.45
}
```

`max_cost_usd` is your cap, the most this request may cost (it lists at $0.30). Poll `GET /v1/generations/{id}` until `status` is `succeeded` or `failed`, then download `GET /v1/generations/{id}/content`. Full API: https://revana.si/llms.txt

## Similar models

- [Kling 4.0](https://revana.si/models/kling-4.0.md): from $0.08 per second of video
- [Kling 3.0](https://revana.si/models/kling-3.0.md): from $0.09 per second of video
- [Kling 2.6 Pro](https://revana.si/models/kling-2.6-pro.md): from $0.07 per second of video
- [Kling 2.1 Master](https://revana.si/models/kling-2.1-master.md): from $0.20 per second of video
- [Kling 2.1 Pro](https://revana.si/models/kling-2.1-pro.md): from $0.07 per second of video
- [Kling 2.1 Standard](https://revana.si/models/kling-2.1-std.md): from $0.04 per second of video