HTTP vs. WebSocket

SLNG exposes every TTS and STT model over both HTTP and WebSocket. The URL stays the same; only the protocol changes.

At a Glance

	HTTP	WebSocket
Flow	Request → wait → complete response	Open connection → stream both ways
Latency	200–500 ms	Sub-100 ms
Best for	Batch jobs, file conversion	Voice agents, live transcription
Complexity	One `curl` call	Connection lifecycle to manage

How Each Protocol Works

HTTP
WebSocket

You send a request and get back the full result once processing finishes.Use HTTP when you:

Generate audio files for download or storage
Transcribe pre-recorded audio files
Want the simplest possible integration
Don’t need real-time streaming

curl https://api.slng.ai/v1/tts/slng/deepgram/aura:2 \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "text": "Hello from HTTP!" }' \
  --output hello.wav

See complete examples: TTS over HTTP · STT over HTTP

You open a persistent connection and stream data in both directions.Use WebSocket when you:

Build voice agents (STT + LLM + TTS in a loop)
Need real-time transcription from a microphone
Want the lowest possible latency
Stream audio continuously

const ws = new WebSocket("wss://api.slng.ai/v1/tts/slng/deepgram/aura:2");

ws.onopen = () => {
  ws.send(JSON.stringify({ type: "text", text: "Hello from WebSocket!" }));
};

ws.onmessage = (event) => {
  if (event.data instanceof ArrayBuffer) {
    playAudio(event.data); // Stream audio as it arrives
  }
};

See complete examples: TTS over WebSocket · STT over WebSocket

WebSocket Best Practices

WebSocket connections are stateful — you need to handle the lifecycle:

Reconnect with backoff. If the connection drops, retry with exponential delay (1s, 2s, 4s… up to 30s).
Handle binary and text frames. Audio arrives as binary ArrayBuffer; control messages come as JSON text.
Send a close frame when you’re done so the server releases resources.

Which Protocol for Which Use Case?

Use case	Protocol	Why
Convert a script to an audio file	HTTP	One request, one file — simple
Transcribe a batch of recordings	HTTP	Upload each file, get results
Voice agent (phone or web)	WebSocket	Real-time STT→LLM→TTS loop
Live captioning / transcription	WebSocket	Stream mic audio, get text back
Generate a voiceover for a video	HTTP	No real-time requirement

Next Steps

TTS over HTTP

Generate audio files from text with simple HTTP requests.

TTS over WebSocket

Stream audio in real-time with interruption support.

STT over HTTP

Transcribe pre-recorded audio files.

STT over WebSocket

Transcribe live audio from a microphone.

Getting Started

Dashboard

Guides

Voices

Examples

At a Glance

How Each Protocol Works

WebSocket Best Practices

Which Protocol for Which Use Case?

Next Steps

TTS over HTTP

TTS over WebSocket

STT over HTTP

STT over WebSocket

Getting Started

Dashboard

Guides

Voices

Examples

​At a Glance

​How Each Protocol Works

​WebSocket Best Practices

​Which Protocol for Which Use Case?

​Next Steps

TTS over HTTP

TTS over WebSocket

STT over HTTP

STT over WebSocket

At a Glance

How Each Protocol Works

WebSocket Best Practices

Which Protocol for Which Use Case?

Next Steps