Modulate
#1 STT API on Hugging Face's ASR Leaderboard

Looking for an Assembly AI alternative?

Get the same bundled intelligence, plus audio-native signals Assembly AI can't offer, including emotion and accent detection, at a lower cost and with higher accuracy with Modulate's speech-to-text API.

"This transcription model might be the best stuff I've seen. I've never seen another model with realtime diarization (that works?!)"
NL
Nick Leonard
CEO, VoiceRun
Free tier · no card needed
Get immediate API access
400 hours free. Start transcribing in minutes.
400 hours free · $0.03/hr after
independent benchmarks

Assembly AI vs. Modulate's Speech-to-Text API

Tested on Earnings-22, and VoxPopuli datasets, Modulate's transcription API achieves a lower Word Error Rate (WER) than Assembly AI, and at the lowest price per hour in the market - $0.03 / hr batch.

Transcription Benchmark (Accuracy vs. Price)
Average Word Error Rate (WER) across Earnings-22 and VoxPopuli datasets
Lowest WER lowest cost
Cost per hour
Avg. Word Error Rate
modulate-transcribe
scribe-v2
assemblyai-universal-2
assemblyai-universal-3-pro
speechmatics-enhanced
google-gemini-2.5-pro
gpt-4o-transcribe
google-chirp-2
deepgram-nova-3
openai-whisper-large-v3
8
9
10
11
12
13 %
$0.00
0.10
0.20
0.30
$0.40
Speech-to-text api Capabilties

Everything you rely on today, plus audio-native signals Assembly AI
can't give you.

Trained on 500M+ hours of noisy, real-world audio, Modulate's models were built to not only understand what's being said, but how - including the emotion and tone behind the words.

✓
Real-time diarization included at base pricing - Get speaker-separated transcripts out of the box.
✓
Emotion and accent detection included free - 20+ emotions, 20+ accents, detected directly from audio, not inferred from words.
✓
Multilingual support - 70+ languages and dialects supported.
✓
PII/PHI tagging included, regardless of which base model you're on. No add-on or post-processing step.
✓
REST batch and WebSocket streaming - same key, same endpoint pattern
Explore the docs →
bash
curl --request POST \
  --url https://platform.modulate.ai/api/velma-2-stt-batch \
  --header 'Content-Type: multipart/form-data' \
  --header 'X-API-Key: <api-key>' \
  --form upload_file='@example-file' \
  --form speaker_diarization=true \
  --form emotion_signal=false \
  --form accent_signal=false \
  --form deepfake_signal=false \
  --form pii_phi_tagging=false
200 OK
JSON response
312ms
{
  "text": "Hello, how are you? Bonjour, ça va?",
  "duration_ms": 5000,
  "utterances": [
    {
      "utterance_uuid": "e5f6a7b8-c9d0-1234-efab-345678901234",
      "text": "Hello, how are you?",
      "start_ms": 0,
      "duration_ms": 2000,
      "speaker": 1,
      "language": "en",
      "emotion": "Neutral",
      "accent": "American",
      "deepfake_score": null
    },
    {
      "utterance_uuid": "f6a7b8c9-d0e1-2345-fabc-456789012345",
      "text": "Bonjour, ça va?",
      "start_ms": 2500,
      "duration_ms": 2500,
      "speaker": 2,
      "language": "fr",
      "emotion": "Happy",
      "accent": "British",
      "deepfake_score": null
    }
  ]
}
Modulate transcription pricing

Transparent. On-demand. No lock-in.

No contracts, no volume minimums. Pay only for what you process.

Batch · REST APIUSD / hour processed
Modulate lowest cost
modulate-transcribe
$0.03
xAI
grok-stt
$0.10
AssemblyAI
universal-3 Pro
$0.21
ElevenLabs
scribe v2
$0.22
Deepgram
nova-3
$0.31
OpenAI
gpt-4o-transcribe
$0.36
Streaming · WebSocketUSD / hour live audio
Modulate lowest cost
modulate-transcribe
$0.06
xAI
grok
$0.20
Speechmatics
enhanced
$0.24
Deepgram
nova-3
$0.35
OpenAI
gpt-4o-transcribe
$0.36
AssemblyAI
universal-3-pro
$0.45
get started free

400 free hours.
No credit card required.

Start transcribing in under 5 minutes. Full docs included.

Get API Key Free →Explore the Docs

No commitment. No sales call. Scales to hundreds of hours.