API

Deepgram API

Build with Deepgram's speech-to-text, text-to-speech, voice agent, and audio intelligence APIs.

"Flux" names two separate products. Flux STT is conversational speech-to-text on /v2/listen (model=flux-general-en). Flux TTS is turn-based speech synthesis on /v2/speak (model=flux-{voice}-{language}). They share a name and a design philosophy — turn-aware, built for voice agents — but they are different endpoints with different models, params, and messages. When a request just says "Flux", check whether it is about transcribing audio or producing it.

Getting Started

All API requests require authentication via API key or JWT:

• API Key: Authorization: Token <API_KEY>
• JWT: Authorization: Bearer <JWT>

Base servers:

• REST & STT/TTS WebSocket: https://api.deepgram.com
• Voice Agent WebSocket: https://agent.deepgram.com

How Deepgram's APIs Fit Together

                   ┌──────────────────────────────┐
                   │       api.deepgram.com        │
                   └──────────────────────────────┘
                                │
  ┌───────────┬───────────┬─────┴─────┬───────────┬───────────┐
  ▼           ▼           ▼           ▼           ▼           ▼
  /v1/listen  /v2/listen  /v1/speak   /v2/speak   /v1/read    /v1/projects/*
  Nova — STT  Flux — STT  Aura — TTS  Flux — TTS  Text AI     Management
  REST + WSS  WSS only    REST + WSS  REST + WSS  REST only   REST only

                   ┌──────────────────────────────┐
                   │      agent.deepgram.com       │
                   └──────────────────────────────┘
                                │
                                ▼
                   /v1/agent/converse
                   WebSocket only
                   audio ──▶ STT ──▶ LLM ──▶ TTS ──▶ audio
                   (Deepgram orchestrates the full pipeline)

Which API Should I Use?

Audio → text (transcription)?
├─ General-purpose transcription (captions, batch, call logs, live streams with custom turn logic)
│  └─ Nova models via /v1/listen
│     ├─ Pre-recorded file    →  REST  POST https://api.deepgram.com/v1/listen?model=nova-3
│     └─ Live stream          →  WSS   wss://api.deepgram.com/v1/listen?model=nova-3
│
└─ Conversational audio / voice-agent-style turn detection
   └─ Flux STT models via /v2/listen
      └─ Live stream          →  WSS   wss://api.deepgram.com/v2/listen?model=flux-general-en

Text → audio (speech synthesis)?
├─ General-purpose TTS (broadest voice catalog, compressed/containerized audio)
│  └─ Aura models via /v1/speak
│     ├─ One-shot             →  REST  POST https://api.deepgram.com/v1/speak?model=aura-2-thalia-en
│     └─ Low-latency stream   →  WSS   wss://api.deepgram.com/v1/speak?model=aura-2-thalia-en
│
└─ Voice-agent TTS (turn-based lifecycle, barge-in, cross-turn consistency)
   └─ Flux TTS models via /v2/speak  — model is REQUIRED, and must be flux-*
      ├─ Pre-render a block   →  REST  POST https://api.deepgram.com/v2/speak?model=flux-alexis-en
      └─ Live conversation    →  WSS   wss://api.deepgram.com/v2/speak?model=flux-alexis-en

Full conversational voice agent (audio in, audio out)?
└─ WSS wss://agent.deepgram.com/v1/agent/converse
   Deepgram handles STT + your configured LLM + TTS internally

Analyze text for insights?
└─ REST POST /v1/read
   (summaries, sentiment, topics, intents)

Speech-to-Text: Nova (/v1/listen) vs Flux STT (/v2/listen)

Both model families are actively maintained and industry-leading. They solve different problems — pick the one that matches your use case.

Pick Nova (/v1/listen, model=nova-3) when:

• Generating captions, subtitles, or transcripts for recorded media
• Running batch transcription over files (REST)
• You need analytics overlays (summarize, sentiment, topics, intents, diarize, redact)
• You want WebSocket streaming with your own turn-detection logic

Pick Flux STT (/v2/listen, model=flux-general-en) when:

• Building an interactive voice agent or assistant
• You want end-of-turn detection handled for you
• You need low-latency turn signals and barge-in support
• You want to update EOT thresholds or keyterms mid-session without reconnecting

Migrating from Nova 3 to Flux STT? See the official Nova 3 → Flux migration guide.

Text-to-Speech: Aura (/v1/speak) vs Flux TTS (/v2/speak)

Both TTS families are actively maintained. /v2/speak is a new endpoint, not a replacement — /v1/speak is unchanged, and there is no aliasing, redirect, or deprecation. The families do not overlap: Aura voices are served only on /v1/speak, Flux TTS voices only on /v2/speak.

Pick Aura (/v1/speak) when:

• You need a language other than English, or a specific Aura voice
• You want compressed or containerized output (mp3, opus, flac, aac) from a stream
• You're doing one-shot synthesis and don't need a turn lifecycle
• You're already on Aura and nothing in Flux TTS is pulling you over — v1 is unchanged

Pick Flux TTS (/v2/speak) when:

• Building a voice agent, phone assistant, or customer-service bot
• You're streaming LLM tokens to a speaker in real time and want the lowest time-to-first-audio
• The user may barge in mid-response and you need to know what they actually heard
• You want tone to carry across turns without managing state yourself
• You're pre-rendering fixed audio (IVR prompts, notifications) with a Flux TTS voice — use the batch REST transport

Migrating from Aura? See the official Migrating from Aura to Flux TTS guide and Batch vs Streaming.

API Domains

Common Mistakes to Avoid

All APIs

1. Feature flags are query params — except for Voice Agent and the v2 mid-session updates. For /v1/listen, /v2/listen, /v1/speak, and /v2/speak, initial options go on the URL. The request body carries only audio data (REST) or audio frames (WebSocket). Exceptions: /v1/agent/converse has no URL query params at all (all config goes in the Settings message); /v2/listen supports a Configure message after connection to update EOT thresholds and keyterms mid-session; and /v2/speak supports a Configure message that updates speed only. Also note that /v2/listen has a much smaller param set than /v1/listen — flags like smart_format, diarize, and punctuate are not available.

2. Rate limits are concurrent connections, not total requests. A 429 means too many simultaneous open connections, not too high a request volume. Diarization and other compute-heavy features reduce your concurrency allowance further.

STT WebSocket (/v1/listen)

3. Send KeepAlive as a text frame, not binary. The connection closes after 10 seconds of no audio. Send {"type":"KeepAlive"} as a text (JSON) frame every 3–5 seconds during silence. Sending it as a binary frame causes transcription delays — the audio pipeline chokes — not a silent no-op.

4. Never send empty byte payloads. Sending a zero-length binary frame to /v1/listen is treated as a close — it terminates the connection. Always check that your audio packet has length before sending.

5. encoding must match the actual audio format. If encoding=linear16 but you're sending opus, you'll get a DATA-0000 error or garbled output. Omit encoding entirely when sending containerized formats (mp3, wav, ogg) — Deepgram detects them automatically.

6. Timestamps reset on reconnect. Each new WebSocket connection restarts timestamps at 00:00:00. For real-time apps, maintain a timestamp offset across reconnections or you'll silently corrupt your transcript timeline.

TTS WebSocket (/v1/speak)

7. Don't send empty text. A Speak message with an empty text field returns a 400 error. Always validate input before sending.

8. Character rate limiting (DATA-0001) means slow down, not retry. If you hit this, reduce how fast you're submitting text chunks — don't immediately retry or you'll compound the problem.

Flux TTS (/v2/speak)

9. model is required, and must be a flux-* voice. Unlike /v1/speak there is no default — a connection or request without model is rejected. Aura strings are rejected on /v2/speak, and Flux voices are not served by /v1/speak; the two families never mix. Model strings are flux-{voice}-{language}, e.g. flux-alexis-en. There is no version segment — generations roll forward behind a stable name, as with Flux STT.

10. Flush ends the turn — it is not a v1-style buffer flush. There is no Finalize; it's folded into Flush. Audio starts streaming on its own before you flush, so don't wait to send text. Use the turn's SpeechMetadata (not Flushed) as your end-of-turn signal — it arrives once all of the turn's audio has been sent, and carries the billing and timing counts, so you can drop client-side character or duration tracking. The server assigns the turn's speech_id; never send one yourself.

11. Streaming is raw audio only, and rejects anything it doesn't recognize. The WebSocket emits non-containerized audio, so encoding is limited to linear16 (default), mulaw, or alaw. The compressed and containerized encodings (mp3, opus, flac, aac) and the container, bit_rate, callback, callback_method, and priority params are batch-only — sending them to the socket fails the connection, as does any unknown or misspelled param. Use the batch REST transport when you need compressed output.

12. Insert whitespace between separate generations — the server won't. Text normalization runs before synthesis, but successive Speak messages are concatenated verbatim. Sending "Hello world." then "How are you?" is processed as "Hello world.How are you?", which causes sentence-boundary artifacts. Add a single space (or the right separator for non-whitespace languages) when you stitch a reply, a tool-call result, and another reply together. Send plain text: SSML and other markup is stripped, with an INPUT_MARKUP_STRIPPED warning.

Voice Agent (/v1/agent/converse)

13. Send the Settings message before any audio. The agent ignores everything until it receives and acknowledges the Settings configuration. Message ordering is strictly required.

14. agent.speak.provider.version selects the TTS family — and omitting agent.speak now gives you Flux TTS. Set version to v2 for Flux TTS or v1 for Aura; when you specify a provider but omit version, it defaults to v1. But if you omit agent.speak entirely, the agent defaults to Flux TTS with the flux-kit-en voice. Switch families by changing version and model together — a flux-* model under v1, or an aura-* model under v2, is invalid:

    { "agent": { "speak": { "provider": { "type": "deepgram", "version": "v2", "model": "flux-alexis-en" } } } }
    

Flux STT model (/v2/listen)

15. Use /v2/listen and model=flux-general-en. /v1/listen does not support Flux STT. model=flux alone is not a valid value. Do not include language or encoding params for containerized audio.

16. Use Configure to update EOT thresholds and keyterms mid-session. Unlike /v1/listen, Flux STT supports live reconfiguration after connection — no need to reconnect to change turn detection sensitivity or boost new keyterms:

    { "type": "Configure", "thresholds": { "eot_threshold": "0.8", "eot_timeout_ms": "3000" }, "keyterms": ["Deepgram"] }
    

    The server responds with ConfigureSuccess (echoing back applied values) or ConfigureFailure. Omitted threshold fields keep their current values.

Authentication

17. JWT TTL applies only to the initial handshake. Tokens default to 30 seconds. Once the WebSocket connection is established, the token expiring does not close it — tokens are only needed for the upgrade request.

SDK-Specific Skills

This api skill covers the product contracts (endpoints, query params, message shapes) that are identical across SDKs. For language-idiomatic code — imports, async patterns, builder APIs, common errors — install the SDK-specific skills. Each Deepgram SDK publishes 7 product skills named deepgram-{lang}-{product} (e.g. deepgram-python-speech-to-text, deepgram-js-voice-agent) plus a maintainer skill deepgram-{lang}-maintaining-sdk. The deepgram-{lang}- prefix avoids collisions when you install skills from multiple SDKs.

# Install all skills from a specific SDK
npx skills add deepgram/deepgram-python-sdk     # Python
npx skills add deepgram/deepgram-js-sdk         # JavaScript / TypeScript
npx skills add deepgram/deepgram-java-sdk       # Java
npx skills add deepgram/deepgram-go-sdk         # Go
npx skills add deepgram/deepgram-rust-sdk       # Rust
npx skills add deepgram/deepgram-swift-sdk      # Swift
npx skills add deepgram/deepgram-kotlin-sdk     # Kotlin
npx skills add deepgram/deepgram-dotnet-sdk     # C# / .NET
npx skills add deepgram/deepgram-browser-sdk    # Browser TypeScript

# Or install a specific product skill from one SDK (note the deepgram-{lang}- prefix)
npx skills add deepgram/deepgram-python-sdk --skill deepgram-python-speech-to-text
npx skills add deepgram/deepgram-js-sdk     --skill deepgram-js-voice-agent

Related Deepgram skills

Documentation

• API Reference
• Speech-to-Text Getting Started
• Text-to-Speech Docs (Aura)
• Flux TTS Overview
• Voice Agent Docs
• Voice Agent TTS Models
• Audio Intelligence
• Self-Hosted Deployments