Speech-to-text API comparison
Compare Soniox, Deepgram, AssemblyAI, OpenAI, Google, Azure, and Speechmatics side by side, on the same audio, in real time. See accuracy, latency, multilingual handling, and feature differences.
Why compare STT providers
Not all speech-to-text systems handle real-world audio the same way. The differences become clear when you test the conditions production systems face daily.
Accents get misheard by some providers and transcribed accurately by others. Overlapping speakers blur into a single stream. Conversations that switch languages mid-sentence fall apart. Background noise and domain-specific terms trip up models that look solid in clean demos. And latency varies wildly, some providers stream word by word, others deliver transcripts in laggy chunks that make real-time interfaces feel broken.
This comparison tool lets you hear exactly how each provider transcribes the same audio, side by side. No marketing claims. Just direct, real-time transcription on the inputs that matter for your use case.
The above demo isn’t static. It’s a real call to every provider’s API, in real time. We did our best to make every provider do its best. We built this framework because so many of our customers had to do this comparison themselves, and then chose Soniox. We open sourced it, so you can see and use the code yourself.
Everything you see here is reproducible. The full framework is open-source.
graph_8Fork it on GithubHow to evaluate a speech-to-text API
Accents and real-world audio
Many providers perform well on clean English and fall apart on regional accents, background noise, and everyday microphones. Play the same clip through each API and listen for words that change depending on the speaker.
Language switching mid-sentence
People mix languages in a single utterance. Some providers require you to pick one language per request. Others detect the shift and transcribe every word in the correct language, with no manual switching.
Alphanumerics and domain terms
Phone numbers, reference IDs, and specialized vocabulary are where accuracy breaks down. Watch how each provider handles digits, codes, and technical terms — the details your product actually depends on.
Real-time streaming latency
For live interfaces, delay is a feature, not a detail. Some providers stream word by word with sub-200ms latency. Others return transcripts in laggy chunks that make voice agents and conversational apps feel broken.
Feature comparison
Feature coverage decides whether a speech-to-text API can actually power your product. Multilingual handling, speaker separation, translation, and data-residency support all live in this layer.
The table below compares Soniox against Deepgram, AssemblyAI, OpenAI Whisper, Google Cloud Speech-to-Text, Microsoft Azure Speech, and Speechmatics across the capabilities that matter in production: a single multilingual model versus per-language models, language hints and automatic language identification, speaker diarization, real-time one-way and two-way translation, word-level timestamps and confidence scores, endpoint detection, manual finalization, and sovereign-cloud deployment for data residency.
| Feature | Soniox stt-rt-v4 | OpenAI gpt-4o-transcribe | Google chirp_2 | Azure en-US-Conversation | Speechmatics realtime-enhanced | Deepgram nova-3 | AssemblyAI Universal |
|---|---|---|---|---|---|---|---|
Speech-to-text API pricing comparison
Headline rates don't tell the whole story. Some providers bundle features like diarization, translation, and language identification; others charge for each add-on separately. Some have one flat price; others have a tiered model where the cheap tier loses the features you actually need in production.
The table below shows publicly listed rates as of May 2026, with sources linked. Always factor in add-ons, multichannel billing, and concurrency limits for your actual use case.
| Provider | Real-time / streaming | Batch / async | Translation included | Diarization |
|---|---|---|---|---|
Soniox | $0.12/hr | $0.10/hr | Yes, real-time across 60+ languages | Included |
| Token-based pricing; all features bundled. Source: Soniox pricing page | ||||
Deepgram | Multilingual: $0.348/hr ($0.0058/min) Monolingual: $0.288/hr ($0.0048/min) | Multilingual: $0.552/hr ($0.0092/min) Monolingual: $0.462/hr ($0.0077/min) | Not included (separate service required) | Add-on: +$0.12/hr ($0.0020/min) |
| Add-ons priced separately: Redaction +$0.12/hr, Keyterm Prompting +$0.078/hr. Smart formatting included. Source: Deepgram pricing page | ||||
AssemblyAI | Universal-3 Pro Streaming (6 languages): $0.45/hr Universal-Streaming (English only): $0.15/hr | Universal-3 Pro: $0.21/hr Universal-2: $0.15/hr | Add-on: +$0.06/hr | Batch add-on: +$0.02/hr Streaming add-on: +$0.12/hr |
| Strong audio intelligence add-ons (summarization $0.03/hr, sentiment $0.02/hr, topic detection $0.15/hr). Source: AssemblyAI pricing page | ||||
OpenAI | Not natively streaming (Realtime API is a separate product) | GPT-4o Transcribe & Whisper: $0.36/hr ($0.006/min) GPT-4o Mini Transcribe: $0.18/hr ($0.003/min) | Not included | Not native (GPT-4o Transcribe Diarize variant exists at same base rate) |
| 25 MB upload limit per request. Whisper also available open-source for self-hosting. Source: OpenAI pricing page | ||||
Google Cloud | Standard (first 500K min/month): $0.96/hr ($0.016/min) Above 2M min/month: $0.24/hr ($0.004/min) | Dynamic Batch: $0.18/hr ($0.003/min) | Not included (separate Cloud Translation API required) | Separate billing |
| Each audio channel billed separately. Medical models $4.68/hr ($0.078/min). Source: Google Cloud pricing page | ||||
Azure | Standard real-time: $1.00/hr Custom real-time: $1.20/hr | Standard batch: $0.18/hr Fast transcription: $0.36/hr | Billed separately: $2.50/hr | Real-time add-on: +$0.30/hr Batch: included |
| Commitment tiers can drop standard to ~$0.50/hr at 50K hrs/year. Source: Azure pricing page | ||||
Speechmatics | Pro tier: From $0.24/hr | Pro tier: From $0.24/hr | Add-on (limited language pairs) | Included |
| Free tier 480 min/month. 20% volume discount above 500 hrs/month. Pro tier capped at 6,000 hrs/month. Source: Speechmatics pricing page | ||||
What this means for cost?
For real-time streaming with the features most production apps need (diarization, multilingual handling, and translation) Soniox at $0.12/hr is between 2× and 8× cheaper than the alternatives once their add-ons and required services are factored in. The cheapest headline rate isn't always the cheapest total. Deepgram Nova-3 monolingual streaming looks like $0.288/hr, but it doesn't include translation, diarization adds another $0.12/hr, and you need the more expensive multilingual model ($0.348/hr) the moment your users speak anything other than English.
What this means for features?
Soniox is the only provider in this list that includes real-time transcription, translation, diarization, language identification, and multilingual handling in a single hourly rate. AssemblyAI is the closest match on features but starts at $0.45/hr for the multilingual streaming model. Speechmatics is competitive on price but caps Pro-tier usage at 6,000 hrs/month, which limits scale without an enterprise contract.
All prices reflect publicly listed rates as of May 2026, sourced from each provider's official pricing page. Per-minute rates are converted to per-hour for comparison. Where providers offer tiered or volume pricing, the most commonly used production tier is shown. Enterprise contracts, committed-use discounts, and regional pricing may differ. Add-on features (diarization, redaction, custom vocabulary, language identification, translation) are priced separately by most providers; we've called out the most common ones, but actual cost depends on which features you enable. We update this table when providers change their public pricing — if anything here is out of date, please let us know at support@soniox.com.
Frequently asked questions
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Which speech-to-text API supports the most languages?arrow_downward
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Deepgram vs Soniox: which is better?arrow_downward
AssemblyAI vs OpenAI Whisper: which is better?arrow_downward
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stt-rt-v4. Hear the difference on the comparison tool above with your own audio.Which speech-to-text API supports real-time translation?arrow_downward
Can I self-host a speech-to-text API?arrow_downward
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