New: Soniox v5 Async is here
Get the AppBuild with API

Compare speech-to-text APIs
on your own audio

Compare Soniox, OpenAI, Google, Azure, AssemblyAI, Deepgram, and Speechmatics on the same audio, in real time. See the accuracy difference, then compare pricing and features, before you commit to an API.

See which speech-to-text API is cheapest

Accuracy is only half the decision. The other half is cost. Most speech-to-text APIs charge extra for diarization, translation, and multilingual support, so the headline rate hides the real bill. Soniox is one flat rate with all of it included, nothing billed on top. Set your monthly hours below and see the all-in price, side by side.

Pricing calculator

Stop overpaying for speech AI

Sonioxvs

1,000 hours of audio / month

1025501002505001k2.5k5k10k100k

Pricing assumptions

Based on public pay-as-you-go pricing. Enterprise discounts and committed-use contracts may differ. Some providers charge separately for certain features. The calculator uses the public price for the provider configuration that most closely matches Soniox.

Why compare speech-to-text APIs

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.

These tools let you compare on both axes that decide the choice. The live demo lets you see exactly how each provider transcribes the same audio, side by side. The price calculator above shows what each provider actually costs at your volume, including the diarization, translation, and multilingual add-ons most of them bill on top.

The demo is a real call to every provider’s API, in real time, and the calculator is built on each provider’s published pricing. We did our best to make every provider do its best. We built this because so many of our customers had to run the comparison themselves, and then chose Soniox. We open sourced it, so you can see and use the code yourself.

Everything you see is reproducible. The full framework is open-source.

Fork it on Github

Compare speech-to-text API providers by features

You evaluated the accuracy difference in the demo and saw the price at your volume. The last question is what each speech-to-text API actually ships.

Soniox is the only provider here that bundles transcription, real-time translation, speaker diarization, language identification, and multilingual handling into one model at one rate. The table below compares every capability that decides whether an API can power your product in production.

FeatureSoniox
stt-rt-v4
OpenAI
gpt-4o-transcribe
Google
chirp_2
Azure
en-US-Conversation
Speechmatics
realtime-enhanced
Deepgram
nova-3
AssemblyAI
Universal
Single Multilingual Model
Language Hints
Language Identification
Speaker Diarization
Customization
Timestamps
Confidence Scores
Translation One Way
Translation Two Way
Endpoint Detection
Manual Finalization
Sovereign Cloud
Soniox vs OpenAI | Soniox vs Google | Soniox vs Azure | Soniox vs Deepgram | Soniox vs Speechmatics | Soniox vs AssemblyAI

How 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.

Accents and real-world audio

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.

Language switching mid-sentence

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.

Alphanumerics and domain terms

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.

Real-time streaming latency

Frequently asked questions

What is the most accurate speech-to-text API?
Accuracy depends on language, audio condition, and content type, so there is no single winner across the board. English-only batch tends to favour providers that train heavily on English data, while multilingual conversations, mixed-language speech, names, and alphanumerics are where Soniox is built to lead. In a 2025 study across 60 languages and real-world YouTube audio, Soniox reached 1.25% WER in English compared with 1.71% for Deepgram and 11.1% for AssemblyAI. The fastest way to judge it for your audio is the side-by-side comparison above.
What is the cheapest speech-to-text API?
Headline rates do not tell the full story. Many providers charge separately for translation, diarization, language packs, or real-time access, so the all-in cost is what matters. Soniox includes transcription, real-time translation, speaker diarization, timestamps, and confidence in one rate starting at $0.10 per hour async and $0.12 per hour streaming.
Which speech-to-text API supports the most languages?
Soniox real-time STT supports 60+ languages in a single model with native-speaker accuracy, automatic language identification, and mid-sentence language switching. Several providers list similar language counts, but accuracy drops sharply outside their top-tier languages, and they often require swapping models per language instead of one unified stream.
What is the best speech-to-text API for voice agents?
Voice agents need low-latency streaming, mid-sentence finalization, accurate handling of names and alphanumerics, and resilience to mid-conversation language switching. Soniox is built for that combination across 60+ languages and ships native integrations for Pipecat and LiveKit. See the voice agents use case for more.
What is the best speech-to-text API for call centers?
Call centers need accurate speaker diarization, precision on account IDs and phone numbers, multilingual support for international queues, and predictable pricing at scale. Soniox includes diarization and real-time translation in one price and offers regional deployment in the US, EU, and JP for data residency. See the call center use case for details.
Deepgram vs AssemblyAI: which is better?
They lead in different areas. Deepgram targets English-first real-time at low cost, while AssemblyAI is known for bolt-on audio intelligence features. Neither is built primarily for real-time multilingual production. If multilingual real-time matters, compare both against Soniox: Soniox vs Deepgram and Soniox vs AssemblyAI.
Deepgram vs Soniox: which is better?
Deepgram is competitive on English-only transcription at low cost. Soniox leads on native-speaker accuracy across 60+ languages, real-time translation built into the same STT stream, mixed-language speech, and alphanumeric precision, with translation, diarization, and timestamps bundled in one price. Full side-by-side: Soniox vs Deepgram.
AssemblyAI vs OpenAI Whisper: which is better?
AssemblyAI is a managed API with audio intelligence features. OpenAI Whisper is an open model you can self-host, but it does not stream out of the box and you own the production infrastructure. Neither is built for real-time multilingual production, so it is worth comparing both against Soniox: Soniox vs AssemblyAI and Soniox vs OpenAI.
Is OpenAI Whisper better than Deepgram?
They solve different problems. Whisper is open-source and covers many languages for batch transcription but does not stream natively. Deepgram is a managed real-time API focused on English-first low-cost transcription. For real-time multilingual production, see Soniox vs OpenAI and Soniox vs Deepgram.
Which speech-to-text API has the lowest latency?
Real-time streaming APIs target sub-second token latency, but the metric that matters for voice agents is time-to-finalised-word and reliable mid-sentence endpointing. Soniox real-time STT streams tokens word by word with mid-sentence finalization on stt-rt-v4. See the difference on the comparison tool above with your own audio.
Which speech-to-text API supports real-time translation?
Soniox real-time translation ships as a built-in extension of the same STT stream, in 60+ target languages, returning original and translated text side by side as the speaker talks. Most other providers either do not offer translation or require a separate translation service stitched on top of transcription.
Can I self-host a speech-to-text API?
OpenAI Whisper is open-source and can be self-hosted, but you take on production infrastructure, streaming, and scaling yourself. Soniox offers on-premises deployment and regional cloud deployment in the US, EU, and JP for enterprises that need data residency without giving up real-time performance.

Start building with Soniox

Create an account instantly, or contact us to design a custom package for your business.

Build with API

Documentation

Get up and running in minutes and spend your time building the product, not wrestling with the API.

Explore docs

See what you’ll pay

Pay only for what you use with our flexible pricing. Built to scale with you.

Pricing details