Don't trust benchmarks.
Test on your own audio.
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.
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 GithubCompare 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.
How to evaluate a speech-to-text API
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?
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
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
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:
and
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:
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:
and
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
and
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.
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?
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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