> ## Documentation Index > Fetch the complete documentation index at: https://docs.goenhance.ai/llms.txt > Use this file to discover all available pages before exploring further. # Kling 4.0 Flash Reference to Video > Kling 4.0 Flash reference-to-video. Guide generation with up to **10 reference images** (style, scene, subject) and up to **5 reference videos** (motion, camera work and other features to imitate — the videos are not edited). 720p only, single takes of up to **20 seconds**. **Audio** — every generated video comes with a native audio track. It is always on: the model has no switch for it, so `sound` / `generate_audio` are rejected. Refer to your assets in `prompt` as `<<>>`, `<<>>`, `<<>>` …, numbered from 1 in the order of `image_urls` and `video_urls`. At least one image or video is required. **Pricing** — in tokens (USD at $0.02/token). With reference images only, the price is the same as Kling 4.0 Flash and only the generated seconds are billed. With reference videos, a lower per-second rate applies to **output seconds + max(total reference video seconds, output seconds)**: | references | tokens/s | USD/s | billed seconds | |---|---|---|---| | images only | 5.5715 | $0.11143 | output | | with reference videos | 3.7143 | $0.074286 | output + max(reference videos, output) | The total reference video length is measured from your files before any tokens are charged, and rounded up to a whole second. Reference images are not charged. Examples: - 5 seconds with reference images only: 27.86 tokens (= $0.5572) - 5 seconds with an 8-second reference video: 13 billed seconds, 48.29 tokens (= $0.9658) - 10 seconds with a 5-second reference video: 20 billed seconds, 74.29 tokens (= $1.4858) Returns an `img_uuid`; poll GET /api/v1/jobs/detail (or use `custom_callback_url`) to get the generated video. **Not accepted by this model** (rejected before any tokens are charged): `image_url` / `image_end_url` / `keyframes` (use [Kling 4.0 Flash](/api-reference/video-generations/kling-4-0-flash) for a first frame), reference audio, `sound` / `generate_audio` (audio is always generated), `negative_prompt`, `seed`, `model_params.multi_shot`, and 1080p / 4K. ## OpenAPI ````yaml api-reference/video-generations/openapi-kling-4-0-flash-refs.json POST /api/v1/videos/generations openapi: 3.1.0 info: title: GoEnhance API - Kling 4.0 Flash Reference to Video description: >- Reference-to-video with Kling 4.0 Flash. Same endpoint as the other Kling models; the model is selected by model. version: 1.0.0 servers: - url: https://api.goenhance.ai security: [] paths: /api/v1/videos/generations: post: tags: - VideoGenerations summary: Kling 4.0 Flash Reference to Video description: >- Kling 4.0 Flash reference-to-video. Guide generation with up to **10 reference images** (style, scene, subject) and up to **5 reference videos** (motion, camera work and other features to imitate — the videos are not edited). 720p only, single takes of up to **20 seconds**. **Audio** — every generated video comes with a native audio track. It is always on: the model has no switch for it, so `sound` / `generate_audio` are rejected. Refer to your assets in `prompt` as `<<>>`, `<<>>`, `<<>>` …, numbered from 1 in the order of `image_urls` and `video_urls`. At least one image or video is required. **Pricing** — in tokens (USD at $0.02/token). With reference images only, the price is the same as Kling 4.0 Flash and only the generated seconds are billed. With reference videos, a lower per-second rate applies to **output seconds + max(total reference video seconds, output seconds)**: | references | tokens/s | USD/s | billed seconds | |---|---|---|---| | images only | 5.5715 | $0.11143 | output | | with reference videos | 3.7143 | $0.074286 | output + max(reference videos, output) | The total reference video length is measured from your files before any tokens are charged, and rounded up to a whole second. Reference images are not charged. Examples: - 5 seconds with reference images only: 27.86 tokens (= $0.5572) - 5 seconds with an 8-second reference video: 13 billed seconds, 48.29 tokens (= $0.9658) - 10 seconds with a 5-second reference video: 20 billed seconds, 74.29 tokens (= $1.4858) Returns an `img_uuid`; poll GET /api/v1/jobs/detail (or use `custom_callback_url`) to get the generated video. **Not accepted by this model** (rejected before any tokens are charged): `image_url` / `image_end_url` / `keyframes` (use [Kling 4.0 Flash](/api-reference/video-generations/kling-4-0-flash) for a first frame), reference audio, `sound` / `generate_audio` (audio is always generated), `negative_prompt`, `seed`, `model_params.multi_shot`, and 1080p / 4K. parameters: - name: Authorization in: header description: '' required: false example: '{{Authorization}}' schema: type: string requestBody: content: application/json: schema: type: object description: >- Kling 4.0 Flash reference-to-video (reference images and / or reference videos). **Pricing** — per billed second: - images only — 5.5715 tokens ($0.11143) - with reference videos — 3.7143 tokens ($0.074286) properties: model: type: string enum: - kling-4-0-flash-refs description: Model name. Must be `kling-4-0-flash-refs` on this page. prompt: type: string maxLength: 2500 description: >- Text prompt. Required, up to 2500 characters. Refer to assets as `<<>>` / `<<>>` (numbered from 1 by array order); a number with no matching asset is rejected. image_urls: type: array maxItems: 10 items: type: string format: uri description: >- Reference image URLs (up to 10), used as style, scene or subject references. `<<>>` is the first item. Up to 10MB each, width and height at least 300px, aspect ratio between 2:5 and 5:2. Smaller images are upscaled automatically. video_urls: type: array maxItems: 5 items: type: string format: uri description: >- Reference video URLs (up to 5). `<<>>` is the first item. Each video must be at least 3 seconds, and all videos together at most 20 seconds. MP4 or MOV, up to 200MB, height 700-4553px. Adding reference videos switches billing to output + max(reference videos, output) seconds at the reference-video rate (see Pricing). duration: type: integer minimum: 3 maximum: 20 default: 5 description: Output duration in seconds, any integer from 3 to 20. resolution: type: string enum: - 720p default: 720p description: >- Output resolution. Kling 4.0 Flash only supports 720p. `quality` is accepted as a compatible alias. ratio: type: string enum: - '16:9' - '9:16' - '1:1' - '21:9' default: '16:9' description: Aspect ratio of the output. custom_callback_url: type: string format: uri description: >- Optional. A publicly accessible HTTPS URL. When the task status changes (processing / success / failed), GoEnhance sends a POST request to this URL. The request body is identical to the response of GET /api/v1/jobs/detail. If your server does not respond with HTTP 200, the notification is retried up to 3 times, with a 3-second timeout per attempt. example: https://your-server.com/goenhance/callback required: - model - prompt example: model: kling-4-0-flash-refs prompt: >- The woman in <<>> dances in a snowy forest, following the moves and camera of <<>> image_urls: - https://your-cdn.com/character.jpg video_urls: - https://your-cdn.com/dance-reference.mp4 duration: 8 ratio: '9:16' responses: '200': description: '' content: application/json: schema: type: object properties: code: type: integer msg: type: string data: type: object properties: img_uuid: type: string cost: type: number description: >- Tokens deducted for this request. This is the amount actually charged, so it already reflects any discount active on your account and can be lower than the listed price. Tokens are deducted when the task is accepted, and refunded automatically if the generation ends in failure. example: 5.82 required: - img_uuid - cost required: - code - msg - data examples: '1': summary: Success value: code: 0 msg: Success data: img_uuid: c12b656c-747a-44fd-9c80-add79b0c52d5 cost: 5.82 '2': summary: Insufficient tokens value: code: 100 msg: tokens is not enough quota: summary: API key quota exceeded value: code: 101 msg: 'API key quota exceeded: 4990 of 5000 tokens used (monthly)' headers: {} '401': description: '' content: application/json: schema: type: object properties: code: type: integer msg: type: string required: - code - msg examples: '1': summary: Unauthorized value: code: 401 msg: Unauthorized headers: {} deprecated: false security: [] ```` This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.