Universal-3 Pro - Benchmarks & Performance - OpenTranscription

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Universal-3 Pro

Name: Universal-3 Pro
Author: AssemblyAI

AssemblyAI

Batch

AssemblyAI's most powerful speech language model — up to 1000 keyterm phrases

Transcribe with this model Compare in playground

6 languages · benchmarked

Overall Score

67.7

#8 of 28

Word Error Rate

17.50%

Character Error Rate

10.42%

Match Error Rate

16.96%

Word Info Lost

20.27%

Avg Latency

5.5s

Benchmarks Run

Benchmark trend

last 30 runs

Word error rate

9.91%

↓ 42.7% · 30d

3 runs ago

latest

Avg latency

5.7s

↓ 1.0% · 30d

3 runs ago

latest

Cost vs. accuracy

overall WER · 28 models

Universal-3 Pro

field · 27 models

lower-left is better

Performance by category

8 categories

WER

lower is better

Legal

1.8%

Medical

2.6%

Technical

4.0%

Finance

5.6%

Conversational

10.2%

Code-Switching

18.4%

General

20.6%

Noisy Environment

33.9%

Category	WER	CER	MER	WIL	Latency	Benchmarks
Code-Switching	18.40%	12.34%	17.90%	24.53%	8.8s	2
Conversational	10.21%	6.61%	10.09%	12.27%	6.7s	2
Finance	5.63%	2.39%	5.56%	9.12%	4.9s	2
General	20.62%	11.27%	20.62%	23.64%	5.2s	19
Legal	1.79%	1.18%	1.77%	2.10%	6.6s	2
Medical	2.59%	0.93%	2.59%	3.70%	6.7s	2
Noisy Environment	33.85%	24.52%	29.56%	36.78%	3.3s	4
Technical	3.99%	2.80%	3.97%	4.90%	6.5s	2

Performance by accent

5 accents

Accent	WER	Benchmarks
African	26.15%	1
Australian	3.08%	1
Indian	11.11%	1
British	0.00%	1
American	0.00%	1

Pricing

pay per second

Rate

$0.0035

/min

Per-second billing. Bring your own provider key and pay your provider directly — a 5% routing fee applies (first 100 min/mo free).

Set up BYOK

Cost estimator

1 hour

$0.21

10 hours

$2.09

100 hours

$20.88

1,000 hours

$208.80

Billed per second of audio processed.

API & usage

POST /api/v1/transcriptions

Model ID

assemblyai/universal-3-pro

Get an API key

Authenticate every request with your secret API key as a Bearer token. Issue a key from your dashboard.

Quickstart

Upload your audio, create a job with this model, then poll the job or set a webhook_url to be notified when it completes.

# 1. Request a signed upload URL
curl https://opentranscription.io/api/v1/uploads \
  -H "Authorization: Bearer $OT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{ "file_name": "interview.mp3", "file_size": 3456789, "mime_type": "audio/mpeg" }'
# → { "upload_url": "...", "file_path": "...", "expires_at": "..." }

# 2. Upload the audio bytes to the signed URL
curl -X PUT "$UPLOAD_URL" --upload-file interview.mp3

# 3. Create the transcription job
curl https://opentranscription.io/api/v1/transcriptions \
  -H "Authorization: Bearer $OT_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "file_path": "$FILE_PATH",
    "model": "assemblyai/universal-3-pro",
    "language": "de",
    "diarization": true,
    "webhook_url": "https://your-app.com/webhooks/ot"
  }'
# → we POST a signed event to your webhook_url when the job finishes — no polling required

Key parameters

file_path

string

required

Storage path returned by the upload step.

model

string

required

The model to run this job on.

language

string

ISO 639-1 language code. Omit to auto-detect.

diarization

boolean

Label speakers (A, B, …) in the output.

webhook_url

string

HTTPS URL notified with the result when the job completes. Delivered events are signed (X-OT-Signature).

Response

A completed job returns the transcript in the OpenTranscription Unified Schema (OTUS).

{
  "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
  "status": "completed",
  "transcript": {
    "text": "Welcome to the meeting, everyone.",
    "language": "en",
    "confidence": 0.97,
    "segments": [
      {
        "id": 0,
        "start": 0,
        "end": 3.5,
        "text": "Welcome to the meeting, everyone.",
        "speaker": "A"
      }
    ],
    "words": [
      {
        "word": "Welcome",
        "start": 0,
        "end": 0.42,
        "confidence": 0.99
      }
    ]
  }
}

Webhooks — skip polling

We POST a signed event to your webhook_url when a job completes or fails; verify the X-OT-Signature (HMAC-SHA256, reject if older than 300 s) and dedupe on the event id, then fetch the full transcript via GET /api/v1/transcriptions/{id}.

# We POST a signed event to your webhook_url when a job finishes.
# Headers:
#   X-OT-Signature: t=1736937042,v1=5257a869e7eceb6c6c2c2a1b4d6e9f8c2a1b4d6e9f8c2a1b4d6e9f8c2a1b4d6e
#   X-OT-Event-Id: evt_9f8c2a1b4d6e
#   X-OT-Event-Type: transcription.completed
#
# Body (thin event — fetch the transcript with GET /transcriptions/{data.id}):
{
  "id": "evt_9f8c2a1b4d6e",
  "event": "transcription.completed",
  "created": "2025-01-15T10:30:42.000Z",
  "data": {
    "id": "a1b2c3d4-e5f6-7890-abcd-ef1234567890",
    "status": "completed",
    "error_code": null
  }
}
#
# Verify: HMAC-SHA256 over "<t>.<raw_body>" with your signing secret,
# constant-time compare against any v1, and reject if |now - t| > 300s.

Rate-limited per tier — see the X-RateLimit-* response headers.

Full API reference

Reliability

rolling 30 days

Uptime · 30d

100.00%

Error rate

0.00%

Avg latency

10.4s

Last incident

None in 30d

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Supported Languages

GermanEnglishSpanishFrenchItalianPortuguese

Supported Formats

mp3wavflacm4aoggwebm

Features

Auto-detectDiarizationCode-switching+2

Universal-3 Pro

Benchmark trend

Cost vs. accuracy

Performance by category

Performance by accent

Pricing

API & usage

Reliability

Similar models

About Universal-3 Pro