Best Speech-to-Text API Comparison 2026

# Deepgram Nova-3
curl -X POST "https://api.deepgram.com/v1/listen?model=nova-3&smart_format=true&diarize=true" \
  -H "Authorization: Token $DEEPGRAM_API_KEY" \
  -H "Content-Type: audio/mp3" \
  --data-binary @meeting.mp3

// Node.js
import { createClient } from '@deepgram/sdk';
const deepgram = createClient(process.env.DEEPGRAM_API_KEY);

const { result } = await deepgram.listen.prerecorded.transcribeFile(
  fs.readFileSync('meeting.mp3'),
  { model: 'nova-3', smart_format: true, diarize: true }
);
console.log(result.results.channels[0].alternatives[0].transcript);

# AssemblyAI Universal-2
# Step 1: Upload file
curl -X POST "https://api.assemblyai.com/v2/upload" \
  -H "authorization: $ASSEMBLYAI_API_KEY" \
  --data-binary @meeting.mp3

# Step 2: Create transcription (use upload_url from step 1)
curl -X POST "https://api.assemblyai.com/v2/transcript" \
  -H "authorization: $ASSEMBLYAI_API_KEY" \
  -H "content-type: application/json" \
  -d '{"audio_url": "https://...", "speaker_labels": true}'

// Node.js
import { AssemblyAI } from 'assemblyai';
const client = new AssemblyAI({ apiKey: process.env.ASSEMBLYAI_API_KEY });

const transcript = await client.transcripts.transcribe({
  audio: './meeting.mp3',
  speaker_labels: true,
  language_detection: true
});
console.log(transcript.text);

# Rev AI Reverb
curl -X POST "https://api.rev.ai/speechtotext/v1/jobs" \
  -H "Authorization: Bearer $REVAI_ACCESS_TOKEN" \
  -H "Content-Type: audio/mp3" \
  --data-binary @meeting.mp3

# Check status and get transcript
curl "https://api.rev.ai/speechtotext/v1/jobs/{id}/transcript" \
  -H "Authorization: Bearer $REVAI_ACCESS_TOKEN" \
  -H "Accept: text/plain"

// Node.js
import { RevAiApiClient } from 'revai-node-sdk';
const client = new RevAiApiClient(process.env.REVAI_ACCESS_TOKEN);

const job = await client.submitJobLocalFile('./meeting.mp3');
// Poll until complete
const transcript = await client.getTranscriptText(job.id);
console.log(transcript);

// OpenAI GPT-4o Transcribe streaming (WebSocket)
const ws = new WebSocket('wss://api.openai.com/v1/realtime?model=gpt-4o-transcribe', {
  headers: { 'Authorization': `Bearer ${process.env.OPENAI_API_KEY}` }
});

ws.on('open', () => {
  ws.send(JSON.stringify({
    type: 'session.update',
    session: { input_audio_transcription: { model: 'gpt-4o-transcribe' } }
  }));
});

ws.on('message', (data) => {
  const event = JSON.parse(data);
  if (event.type === 'conversation.item.input_audio_transcription.completed') {
    console.log('Live:', event.transcript);
  }
});

// Send audio as base64 input_audio_buffer.append events
ws.send(JSON.stringify({ type: 'input_audio_buffer.append', audio: base64Audio }));

// AssemblyAI real-time streaming (Node.js)
import { RealtimeTranscriber } from 'assemblyai';

const transcriber = new RealtimeTranscriber({
  apiKey: process.env.ASSEMBLYAI_API_KEY,
  sampleRate: 16_000
});

transcriber.on('transcript', (transcript) => {
  if (transcript.message_type === 'FinalTranscript') {
    console.log('Live:', transcript.text);
  }
});

await transcriber.connect();

// Stream audio from microphone
recorder.on('data', (audio) => {
  transcriber.sendAudio(audio);
});

# Deepgram with diarization (free for batch)
curl -X POST "https://api.deepgram.com/v1/listen?model=nova-3&diarize=true" \
  -H "Authorization: Token $DEEPGRAM_API_KEY" \
  -H "Content-Type: audio/mp3" \
  --data-binary @meeting.mp3

# Response includes per-word speaker IDs:
# "words": [{"word": "Hello", "speaker": 0, "start": 0.0, "end": 0.5}]

// AssemblyAI with speaker labels (+$0.02/hr)
const transcript = await client.transcripts.transcribe({
  audio: './meeting.mp3',
  speaker_labels: true,
  speakers_expected: 3  // optional hint
});

for (const utterance of transcript.utterances) {
  console.log(`Speaker ${utterance.speaker}: ${utterance.text}`);
}
// Speaker A: Welcome to the meeting
// Speaker B: Thanks for having me