Connection keepalive

Overview

In real-time transcription sessions, it's important to keep the WebSocket connection alive, even during periods when no audio is being streamed — such as during silence, pauses, or voice activity detection (VAD) on the client side.

To support this, Soniox provides a special control message:

{"type": "keepalive"}

Sending this message ensures that your WebSocket session remains active and avoids timing out when no audio is being sent.

When to use keepalive

Use the {"type": "keepalive"} message when:

• You're using client-side VAD and only stream audio during speech
• There's silence or inactivity between utterances
• You want to pause streaming without losing session context

This ensures that:

• The connection remains open
• Session-level context (e.g., speaker labels, language tracking, prompt) is preserved

Keepalive requirements

• You must send a {"type": "keepalive"} message at least once every 20 seconds during periods when you're not sending audio.
• Failure to do so may result in the connection being closed due to inactivity.
• You may send it more frequently (e.g., every 5–10 seconds) if desired.

Example

{"type": "keepalive"}

Send this during idle periods in your stream to avoid timeouts while maintaining context.

Best practices

• Send a keepalive message at least every 20 seconds during silence
• Use alongside {"type": "finalize"} if you're segmenting audio manually
• Maintain your connection across short pauses to preserve context