> ## Documentation Index > Fetch the complete documentation index at: https://heygen-1fa696a7.mintlify.app/llms.txt > Use this file to discover all available pages before exploring further. # Create Lipsync > Replaces the audio on an existing video and re-animates the speaker's lip movements to match the new audio. Use mode: 'speed' for fast output or 'precision' for high-quality lip-sync. ## OpenAPI ````yaml /openapi/external-api.json post /v3/lipsyncs openapi: 3.1.0 info: title: HeyGen External API version: 1.0.0 description: >- HeyGen's external API for programmatic AI video creation. See https://docs.heygen.com for full documentation. contact: name: HeyGen Product Infra url: https://heygen.com servers: - url: https://api.heygen.com description: Production security: - ApiKeyAuth: [] - BearerAuth: [] tags: - name: Video Agent description: Create videos from text prompts using AI - name: Videos description: Create, list, retrieve, and delete videos - name: Voices description: Text-to-speech and voice management - name: Audio description: Search the background-music and sound-effects catalog - name: Video Translate description: Translate videos into other languages - name: User description: Account information and billing - name: Avatars description: List and manage avatars and looks - name: Assets description: Upload files for use in video creation - name: Webhooks description: Manage webhook endpoints and events - name: Lipsync description: Dub or replace audio on existing videos - name: Brand description: >- Brand-related resources — brand kits (colors, fonts, logos) and brand glossaries (custom term translations) paths: /v3/lipsyncs: post: tags: - Lipsync summary: Create Lipsync description: >- Replaces the audio on an existing video and re-animates the speaker's lip movements to match the new audio. Use mode: 'speed' for fast output or 'precision' for high-quality lip-sync. operationId: createLipsyncV3 parameters: - $ref: '#/components/parameters/IdempotencyKey' requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/CreateLipsyncRequest' responses: '200': description: Successful response content: application/json: schema: type: object properties: data: $ref: '#/components/schemas/LipsyncCreateResponse' '400': description: Invalid request parameters content: application/json: schema: type: object properties: error: $ref: '#/components/schemas/StandardAPIError' example: error: code: invalid_parameter message: '''video_url'' is required.' param: video_url doc_url: null '401': description: Authentication failed content: application/json: schema: type: object properties: error: $ref: '#/components/schemas/StandardAPIError' example: error: code: authentication_failed message: Invalid or expired API key. Verify your x-api-key header. param: null doc_url: null '409': $ref: '#/components/responses/IdempotencyInProgress' '429': description: Rate limit exceeded content: application/json: schema: type: object properties: error: $ref: '#/components/schemas/StandardAPIError' example: error: code: rate_limit_exceeded message: >- Too many requests. Retry after the duration specified in the Retry-After header. param: null doc_url: null headers: Retry-After: description: Seconds to wait before retrying schema: type: integer security: - ApiKeyAuth: [] - BearerAuth: [] components: parameters: IdempotencyKey: name: Idempotency-Key in: header required: false description: >- Optional client-supplied key for safely retrying mutations. Subsequent calls within 24 hours that share this key replay the original response — even if the request body differs slightly (a warning is logged). A retry that arrives while the original is still in flight gets a 409 `request_in_progress`. Keys must be 1–255 characters from `[A-Za-z0-9_:.-]`; a UUID is a safe default. Scope is per-endpoint and per-resource: the same key on a different route or path parameter is independent. schema: type: string pattern: ^[A-Za-z0-9_\-:.]{1,255}$ maxLength: 255 minLength: 1 example: 550e8400-e29b-41d4-a716-446655440000 schemas: CreateLipsyncRequest: additionalProperties: false description: Request body for POST /v3/lipsyncs. properties: video: description: >- Source video — provide as {type: 'url', url: '...'} or {type: 'asset_id', asset_id: '...'} discriminator: mapping: asset_id: $ref: '#/components/schemas/AssetId' url: $ref: '#/components/schemas/AssetUrl' propertyName: type oneOf: - $ref: '#/components/schemas/AssetUrl' - $ref: '#/components/schemas/AssetId' title: Video audio: description: >- Replacement audio — provide as {type: 'url', url: '...'} or {type: 'asset_id', asset_id: '...'} discriminator: mapping: asset_id: $ref: '#/components/schemas/AssetId' url: $ref: '#/components/schemas/AssetUrl' propertyName: type oneOf: - $ref: '#/components/schemas/AssetUrl' - $ref: '#/components/schemas/AssetId' title: Audio title: anyOf: - type: string - type: 'null' default: null description: Title for the lipsync job title: Title mode: $ref: '#/components/schemas/VideoTranslationMode' default: speed description: >- Quality mode: 'speed' (faster) or 'precision' (higher quality, uses avatar inference) callback_url: anyOf: - type: string - type: 'null' default: null description: Webhook URL for completion notifications title: Callback Url callback_id: anyOf: - type: string - type: 'null' default: null description: ID included in webhook payload title: Callback Id enable_caption: default: false description: Generate captions for the output video title: Enable Caption type: boolean keep_the_same_format: anyOf: - type: boolean - type: 'null' default: null description: Preserve the source video's encoding specs (resolution, bitrate). title: Keep The Same Format enable_dynamic_duration: default: true description: Allow dynamic duration adjustment title: Enable Dynamic Duration type: boolean disable_music_track: default: false description: Remove background music title: Disable Music Track type: boolean enable_speech_enhancement: default: false description: Enhance speech quality title: Enable Speech Enhancement type: boolean enable_watermark: default: false description: Add watermark to output title: Enable Watermark type: boolean start_time: anyOf: - type: number - type: 'null' default: null description: Start time in seconds for partial lipsync title: Start Time end_time: anyOf: - type: number - type: 'null' default: null description: End time in seconds for partial lipsync title: End Time fps_mode: anyOf: - type: string - type: 'null' default: null description: 'Frame rate mode: ''vfr'', ''cfr'', or ''passthrough''.' title: Fps Mode folder_id: anyOf: - type: string - type: 'null' default: null description: Project/folder ID to organize lipsync into title: Folder Id required: - video - audio title: CreateLipsyncRequest type: object LipsyncCreateResponse: description: Response for POST /v3/lipsyncs. properties: lipsync_id: description: Lipsync ID — use GET /v3/lipsyncs/{id} to poll status title: Lipsync Id type: string required: - lipsync_id title: LipsyncCreateResponse type: object StandardAPIError: type: object properties: code: type: string description: Machine-readable error code example: invalid_parameter message: type: string description: Human-readable error message example: Video not found param: type: - string - 'null' description: Which request field caused the error doc_url: type: - string - 'null' description: Link to error documentation required: - code - message AssetId: additionalProperties: false description: Asset input via HeyGen asset ID from the asset upload endpoint. properties: type: const: asset_id description: Input type discriminator title: Type type: string asset_id: description: HeyGen asset ID from the asset upload endpoint title: Asset Id type: string required: - type - asset_id title: AssetId type: object AssetUrl: additionalProperties: false description: Asset input via publicly accessible HTTPS URL. properties: type: const: url description: Input type discriminator title: Type type: string url: description: Publicly accessible HTTPS URL for the asset title: Url type: string required: - type - url title: AssetUrl type: object VideoTranslationMode: enum: - speed - precision title: VideoTranslationMode type: string responses: IdempotencyInProgress: description: >- A prior request with this Idempotency-Key is still in progress. Wait for the original request to complete, then retry. content: application/json: schema: type: object properties: error: $ref: '#/components/schemas/StandardAPIError' example: error: code: request_in_progress message: >- A request with this Idempotency-Key is already in progress. Retry shortly. param: null doc_url: null securitySchemes: ApiKeyAuth: type: apiKey in: header name: x-api-key description: HeyGen API key. Obtain from your HeyGen dashboard. BearerAuth: type: http scheme: bearer description: OAuth2 bearer token. ````