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Compare the speech-to-text APIs on the same audio, side by side, in real time. See which model actually gets your speech right. Then compare pricing and features before you commit.

See which speech-to-text API is cheapestAccuracy is only half the decision. Cost is the other half.

Most speech-to-text APIs charge extra for diarization, multilingual support, or other production features, so the headline price is not always the real price. Soniox uses one flat rate with everything included, no add-ons, no hidden feature fees. Set your monthly hours below and compare 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 yourself

Not all speech-to-text systems handle real-world audio the same way. The differences become obvious when you test the conditions production systems face every day.

Accents get misheard by some providers and transcribed accurately by others. Overlapping speakers blur into a single stream. Conversations that switch languages mid-sentence break down. Background noise, names, numbers, and domain-specific terms trip up models that look strong in clean demos. Latency also varies widely: some providers stream words as they are spoken, while others return transcripts in delayed chunks that make real-time interfaces feel broken.

These tools let you compare the two things that matter most: accuracy and cost. The live demo shows how each provider transcribes the same audio, side by side, in real time. The price calculator shows what each provider actually costs at your volume, including diarization, multilingual support, and other add-ons many providers bill separately.

The demo makes real calls to each provider’s API in real time, and the calculator is based on each provider’s published pricing. We did our best to make every provider perform at its best.

We built this because many of our customers had to run this comparison themselves before choosing Soniox. Now the full framework is open source, so you can inspect it, reproduce it, and run it yourself.

Everything you see is reproducible.

Fork it on Github

Compare speech-to-text API providers by features

Accuracy and cost are only part of the decision. The final question is what each speech-to-text API can actually do.

Soniox is the only provider here that combines transcription, real-time translation, speaker diarization, language identification, and multilingual speech handling in one model at one flat rate. The table below compares the capabilities that matter when you are choosing an API for production.

FeatureSoniox
stt-rt-v5
OpenAI
gpt-4o-transcribe
Google
chirp_3
Azure
en-US-Conversation
Speechmatics
realtime-enhanced
Deepgram
nova-3
AssemblyAI
universal-3-5-pro
ElevenLabs
scribe-v2-realtime
Cartesia
ink-2
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 | Soniox vs ElevenLabs | Soniox vs Cartesia

How to evaluate a speech-to-text API

Accuracy on real-world audio

Many providers perform well on clean English but fail on regional accents, background noise, everyday microphones, fast speech, and messy conversations. Test the same audio across every API and look for the words that change depending on the speaker, environment, or recording quality.

stt · accuracy
English

Language switching

Real conversations do not stay in one language. People switch languages mid-sentence, mix English with local words, or move between speakers who use different languages. Some providers require you to choose one language per request. Stronger systems detect the shift automatically and transcribe every word in the correct language without manual switching.

stt · language switching

Alphanumeric precision

Phone numbers, reference IDs, addresses, product codes, dates, names, and technical terms are where many systems break down. These details often matter more than generic word accuracy because they are what your product, workflow, or customer support process actually depends on.

stt · alphanumerics

Speaker separation

Speaker diarization is not just an async feature. For meetings, calls, interviews, agents, and multi-speaker conversations, you need to know who said what in real time. Evaluate whether diarization works live, how accurate it is during interruptions and overlapping speech, whether it works across all supported languages, and whether it remains reliable in noisy audio.

stt · diarization

Endpoint detection

Real-time applications need to know when a speaker has finished a thought. Endpoint detection determines how quickly a voice agent can respond, how natural a conversation feels, and how often the system cuts people off too early or waits too long. Compare how fast, accurate, tunable, and language-independent each provider’s endpointing is.

stt · turn-taking

Context

Every production system has names, companies, products, medical terms, legal terms, SKUs, acronyms, and domain vocabulary that generic models do not know in advance. Context should reliably improve recognition of those terms, not work only occasionally. Test how large and flexible the context window is, how easy it is to provide custom terms, and whether spoken context terms are actually recognized correctly in real audio.

stt · context

Real-time streaming latency

For live interfaces, latency is a feature, not a detail. Some providers stream words as they are spoken with very low delay. Others return transcripts in delayed chunks that make voice agents, dictation, captions, and conversational apps feel broken. Measure both first-token latency and final transcript latency, because both affect the user experience.

stt · streaming
012345678901234567890123456789ms

Regional support and compliance

Production systems often need data processed in specific regions for compliance, privacy, or latency reasons. Evaluate whether the provider supports regional deployments, whether customer data stays in the selected region, and whether the API remains low-latency for users in that part of the world. Global coverage only matters if it is fast, reliable, and compliant where your customers actually are.

stt · regions
{ "region": "" }

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 2026 study across 60 languages and real-world YouTube audio, Soniox reached 1.25% WER in English compared with 1.71% for Deepgram and 1.74% 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-v5. 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.

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