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Welcome

The Gradium API provides low-latency, high-quality Text-to-Speech and Speech-to-Text capabilities. This reference documents all available REST and WebSocket endpoints.

OpenAPI Specification

Download the OpenAPI specification file

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Authentication

All API endpoints are authenticated using an API key passed via the x-api-key header:

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Server URL

Use the following base URL for all REST endpoints:
For WebSocket endpoints, use:

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Data residency

api.gradium.ai serves every region: requests are routed to the nearest cluster, with no region-specific URL to configure and no residency commitment. Organizations that need their sessions to stay in one region can opt in to data residency and use eu.api.gradium.ai or us.api.gradium.ai instead (same API, same keys). Each response then reports the residency it got, in the x-gradium-residency header for REST and the residency field of the WebSocket ready message. See Data Residency.