> ## Documentation Index
> Fetch the complete documentation index at: https://evolink.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Veo3.1-Lite Video Generation

> - Veo 3.1 Lite is the low-cost tier of Veo 3.1: text-to-video and first / first-and-last frame image-to-video; no reference images or `4k`
- Billed per second of output video; the rate depends on resolution and whether audio is generated, see [EvoLink model pricing](https://evolink.ai/veo-3-1?model=veo-3.1-lite-generate-preview)
- Asynchronous processing: use the returned task ID to [query task status](/en/api-manual/task-management/get-task-detail)
- Generated video links are valid for 24 hours, please save them promptly



## OpenAPI

````yaml en/api-manual/video-series/veo3.1/veo-3.1-lite-generate-preview-generate.json POST /v1/videos/generations
openapi: 3.1.0
info:
  title: Veo-3.1-Lite-Generate-Preview API
  description: >-
    Create Veo 3.1 Lite video generation tasks, supporting text-to-video,
    first-frame image-to-video and first-and-last-frame image-to-video
  license:
    name: MIT
  version: 1.0.0
servers:
  - url: https://api.evolink.ai
    description: Production
security:
  - bearerAuth: []
tags:
  - name: Video Generation
    description: AI video generation APIs
paths:
  /v1/videos/generations:
    post:
      tags:
        - Video Generation
      summary: Veo-3.1-Lite-Generate-Preview API
      description: >-
        - Veo 3.1 Lite is the low-cost tier of Veo 3.1: text-to-video and first
        / first-and-last frame image-to-video; no reference images or `4k`

        - Billed per second of output video; the rate depends on resolution and
        whether audio is generated, see [EvoLink model
        pricing](https://evolink.ai/veo-3-1?model=veo-3.1-lite-generate-preview)

        - Asynchronous processing: use the returned task ID to [query task
        status](/en/api-manual/task-management/get-task-detail)

        - Generated video links are valid for 24 hours, please save them
        promptly
      operationId: createVideoGeneration
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/VideoGenerationRequest'
            examples:
              text_to_video:
                summary: Text-to-Video
                value:
                  model: veo-3.1-lite-generate-preview
                  prompt: >-
                    A golden retriever puppy running through a sunlit meadow,
                    slow motion, cinematic lighting
              first_and_last_frames:
                summary: First-and-last-frame image-to-video
                value:
                  model: veo-3.1-lite-generate-preview
                  prompt: >-
                    A time-lapse transition from sunrise to sunset over a
                    mountain lake
                  image_urls:
                    - https://example.com/first-frame.jpg
                    - https://example.com/last-frame.jpg
                  generation_type: FIRST&LAST
                  quality: 1080p
                  duration: 8
                  callback_url: https://your-domain.com/webhooks/video-task-completed
      responses:
        '200':
          description: Video generation task created successfully
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/VideoGenerationResponse'
        '400':
          description: Invalid request parameters
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  code: invalid_parameter
                  message: Invalid request parameters
                  type: invalid_request_error
        '401':
          description: Unauthenticated, invalid or expired token
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  code: unauthorized
                  message: Invalid or expired token
                  type: authentication_error
        '402':
          description: Insufficient quota, recharge required
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  code: insufficient_quota
                  message: Insufficient quota. Please top up your account.
                  type: insufficient_quota
        '403':
          description: Access denied
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  code: model_access_denied
                  message: >-
                    Token does not have access to model:
                    veo-3.1-lite-generate-preview
                  type: invalid_request_error
        '429':
          description: Rate limit exceeded
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  code: rate_limit_exceeded
                  message: Too many requests, please try again later
                  type: rate_limit_error
        '500':
          description: Internal server error
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ErrorResponse'
              example:
                error:
                  code: internal_error
                  message: Internal server error
                  type: api_error
components:
  schemas:
    VideoGenerationRequest:
      type: object
      required:
        - model
        - prompt
      properties:
        model:
          type: string
          description: >-
            Video generation model name. `image_start`, `image_end` and
            `model_params` are not accepted on this model (returns `400`)
          enum:
            - veo-3.1-lite-generate-preview
          default: veo-3.1-lite-generate-preview
          example: veo-3.1-lite-generate-preview
        prompt:
          type: string
          description: >-
            Prompt describing the video, up to `2000` tokens. Counted with
            cl100k; tokens are not characters. Google lists English as the
            supported prompt language. EvoLink does not reject requests based on
            prompt language; results in other languages are not guaranteed.
          example: >-
            A golden retriever puppy running through a sunlit meadow, slow
            motion, cinematic lighting
        image_urls:
          type: array
          description: >-
            Input image URLs for image-to-video


            **Notes:**

            - Up to `2` images per request: `1` image is used as the first
            frame, `2` images are used as the first and last frames

            - Image size: no larger than `10 MB`

            - Supported file formats: `.jpg`, `.jpeg`, `.png`
          items:
            type: string
            format: uri
          maxItems: 2
          example:
            - https://example.com/first-frame.jpg
        generation_type:
          type: string
          description: >-
            Generation mode. When omitted it is inferred from the number of
            images:

            - `TEXT`: Text-to-video (input images, if any, are not used)

            - `FIRST&LAST`: First-last frame, 1-2 images


            `REFERENCE` (reference images) is not supported by this model and
            returns `400`
          enum:
            - TEXT
            - FIRST&LAST
        aspect_ratio:
          type: string
          description: >-
            Video aspect ratio. `auto` is the same as omitting `aspect_ratio`:
            no ratio is specified and the model decides
          enum:
            - auto
            - '16:9'
            - '9:16'
        generate_audio:
          type: boolean
          description: >-
            Whether to generate audio, default `true`. Generating audio
            increases the per-second rate
          default: true
        duration:
          type: integer
          description: Video duration in seconds, default `4`. Longer videos cost more
          enum:
            - 4
            - 6
            - 8
          default: 4
        'n':
          type: integer
          description: >-
            Number of videos to generate, default `1`. Each video is billed
            separately
          minimum: 1
          maximum: 4
          default: 1
        quality:
          type: string
          description: >-
            Output resolution, default `720p`. `1080p` has a higher per-second
            rate; `4k` is not supported by this model
          enum:
            - 720p
            - 1080p
          default: 720p
        seed:
          type: integer
          description: Random seed used to reproduce generation results
          minimum: 1
          maximum: 4294967295
        negative_prompt:
          type: string
          description: Negative prompt describing content to exclude from the video
        person_generation:
          type: string
          description: >-
            Person generation control. When omitted, the upstream default is
            `allow_adult`. `allow_adult`: allow adults only; `dont_allow`: do
            not generate videos containing people or faces
          enum:
            - allow_adult
            - dont_allow
        resize_mode:
          type: string
          description: >-
            Image resize mode for image-to-video. When omitted, the upstream
            default is `pad`. `pad`: add padding to fit the output aspect ratio;
            `crop`: center-crop to fit the output aspect ratio. Requires an
            input image; providing this parameter without an image returns `400`
          enum:
            - pad
            - crop
        callback_url:
          type: string
          description: >-
            HTTPS callback URL for task completion


            **Callback Timing:**

            - Triggered when the task is completed or failed

            - Sent after billing confirmation


            **Security Restrictions:**

            - HTTPS protocol only

            - Internal IP addresses are prohibited (127.0.0.1, 10.x.x.x,
            172.16-31.x.x, 192.168.x.x, etc.)

            - URL length must not exceed `2048` UTF-8 bytes


            **Callback Mechanism:**

            - Timeout: `10` seconds

            - Maximum `3` retries after failure (at `1`/`2`/`4` seconds after
            failure)

            - Callback response format is consistent with task query API

            - 2xx status code is considered successful, other codes trigger
            retry
          format: uri
          example: https://your-domain.com/webhooks/video-task-completed
    VideoGenerationResponse:
      type: object
      properties:
        created:
          type: integer
          description: Task creation timestamp
          example: 1757169743
        id:
          type: string
          description: Task ID
          example: task-unified-1757169743-7cvnl5zw
        model:
          type: string
          description: Actual model name used
          example: veo-3.1-lite-generate-preview
        object:
          type: string
          enum:
            - video.generation.task
          description: Specific type of the task
        progress:
          type: integer
          description: Task progress percentage (0-100)
          minimum: 0
          maximum: 100
          example: 0
        status:
          type: string
          description: Task status
          enum:
            - pending
            - processing
            - completed
            - failed
          example: processing
        task_info:
          $ref: '#/components/schemas/VideoTaskInfo'
          description: Video task details
        type:
          type: string
          enum:
            - text
            - image
            - audio
            - video
          description: Output type of the task
          example: video
        usage:
          $ref: '#/components/schemas/VideoUsage'
          description: Usage and billing information
    ErrorResponse:
      type: object
      properties:
        error:
          type: object
          properties:
            code:
              type: string
              description: Error code identifier
            message:
              type: string
              description: Error description message
            type:
              type: string
              description: Error type
    VideoTaskInfo:
      type: object
      properties:
        can_cancel:
          type: boolean
          description: Whether the task can be cancelled
          example: false
        estimated_time:
          type: integer
          description: Estimated completion time (seconds)
          minimum: 0
          example: 600
        video_duration:
          type: integer
          description: Video duration (seconds)
          example: 4
    VideoUsage:
      type: object
      description: Usage and billing information
      properties:
        billing_rule:
          type: string
          description: Billing rule
          enum:
            - per_call
            - per_token
            - per_second
          example: per_call
        credits_reserved:
          type: number
          description: Estimated credits consumed
          minimum: 0
          example: 12.24
        user_group:
          type: string
          description: User group category
          example: default
  securitySchemes:
    bearerAuth:
      type: http
      scheme: bearer
      description: >-
        ## All APIs require Bearer Token authentication ##


        **Get API Key:**


        Visit [API Key Management Page](https://evolink.ai/dashboard/keys) to
        get your API Key


        **Add to request header:**

        ```

        Authorization: Bearer YOUR_API_KEY

        ```

````

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