> ## Documentation Index > Fetch the complete documentation index at: https://docs.opper.ai/llms.txt > Use this file to discover all available pages before exploring further. # Transcribe audio > Transcribe audio to text. By default runs synchronously and returns the transcript inline (200); `audio` accepts a `file_`, an https URL, or a base64 data-URI (max 25MB decoded). Set `stream: true` to receive the transcript live as Server-Sent Events (`transcript.text.delta` chunks then a final `transcript.text.done`, terminated by `data: [DONE]`) — supported on streaming models like `mistral/voxtral-mini-2602`, a 400 otherwise. Set `async: true` to run on the background worker and get a 202 with a status URL to poll instead — use it for long recordings that can exceed the synchronous timeout; it accepts the same `audio` sources (an inline data-URI is staged server-side and deleted after transcription) and lifts the decoded-audio cap to 100MB (a `file_` or https URL is the best way to reach that; a data-URI that large needs a ~133MB request body). `stream` and `async` are mutually exclusive. `model` and `audio` are required; `language` and `prompt` are passed through as hints; `diarize` requests speaker labels (400 on models without diarization support); everything in `parameters` is forwarded verbatim to the provider. See the [Audio guide](/build/multimodal/audio) for runnable examples. ## OpenAPI ````yaml post /v3/audio/transcriptions openapi: 3.1.0 info: description: Schema-driven generative API that orchestrates LLM-powered workflows. title: Task API version: 3.0.0 servers: - description: Production url: https://api.opper.ai - description: Local development url: http://localhost:8080 security: - BearerAuth: [] tags: - description: Schema-driven function management and execution name: Functions - description: OpenAI-compatible chat completions name: Chat - description: OpenAI Responses API compatible endpoint name: Responses - description: Google-compatible interactions endpoint name: Interactions - description: Model registry and capabilities name: Models - description: Synchronous image generation name: Images - description: Text-to-speech and speech-to-text name: Audio - description: Asynchronous video generation name: Videos - description: Reusable file storage for media inputs and generated outputs name: Files - description: Async generation status and downloads name: Artifacts - description: OpenAI-compatible embeddings name: Embeddings - description: Recorded HTTP request/response generations name: Generations - description: System health and status name: System - description: Roundtable endpoint — fan out a query to multiple LLMs and combine results name: Roundtable - description: Web search, fetch, and other utility tools name: Tools - description: Caller identity, credits, and usage name: Account paths: /v3/audio/transcriptions: post: tags: - Audio summary: Transcribe audio (STT) description: >- Transcribe audio to text. By default runs synchronously and returns the transcript inline (200); `audio` accepts a `file_`, an https URL, or a base64 data-URI (max 25MB decoded). Set `stream: true` to receive the transcript live as Server-Sent Events (`transcript.text.delta` chunks then a final `transcript.text.done`, terminated by `data: [DONE]`) — supported on streaming models like `mistral/voxtral-mini-2602`, a 400 otherwise. Set `async: true` to run on the background worker and get a 202 with a status URL to poll instead — use it for long recordings that can exceed the synchronous timeout; it accepts the same `audio` sources (an inline data-URI is staged server-side and deleted after transcription) and lifts the decoded-audio cap to 100MB (a `file_` or https URL is the best way to reach that; a data-URI that large needs a ~133MB request body). `stream` and `async` are mutually exclusive. `model` and `audio` are required; `language` and `prompt` are passed through as hints; `diarize` requests speaker labels (400 on models without diarization support); everything in `parameters` is forwarded verbatim to the provider. operationId: createTranscription requestBody: content: application/json: schema: $ref: '#/components/schemas/TranscriptionRequest' required: true responses: '200': content: application/json: schema: $ref: '#/components/schemas/TranscriptionResponse' description: Successful response '202': content: application/json: schema: $ref: '#/components/schemas/TranscriptionJobResponse' description: >- Accepted – async transcription submitted (async: true). Poll the returned `status_url` (GET /v3/artifacts/{id}/status) for a presigned URL to the transcript JSON when complete. '400': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Bad request '401': description: Unauthorized - missing or invalid API key '500': content: application/json: schema: $ref: '#/components/schemas/ErrorResponse' description: Internal server error components: schemas: TranscriptionRequest: properties: async: type: boolean audio: type: string diarize: type: boolean language: type: string model: type: string parameters: type: object prompt: type: string stream: type: boolean required: - model - audio type: object TranscriptionResponse: properties: created: type: integer duration: type: number id: type: string language: type: string model: type: string segments: items: properties: end: type: number speaker: type: string start: type: number text: type: string required: - start - end - text type: object type: array text: type: string usage: properties: cost: type: number seconds: type: number required: - cost - seconds type: object words: items: properties: end: type: number start: type: number word: type: string required: - word - start - end type: object type: array required: - id - model - created - text - usage type: object TranscriptionJobResponse: properties: id: type: string status_url: type: string required: - id - status_url type: object ErrorResponse: properties: error: properties: code: type: string details: description: Any value message: type: string required: - code - message type: object meta: type: object required: - error type: object securitySchemes: BearerAuth: bearerFormat: API Key description: API key authentication. Pass your API key as a Bearer token. scheme: bearer type: http ````