Japanese to English speech translation API
Stream Japanese (日本語) speech and get English (English) back in real time. One WebSocket, ISO codes ja to en, and ultra-low latency for voice agents and live apps.
Trusted by teams building global voice products
Production-ready Japanese to English translation API
Real Japanese speech includes accents, regional dialects, code switching, and domain-specific vocabulary. Soniox recognizes it in a single model and streams English while the speaker is still talking.
Japanese (Japonic) and English (Indo-European > Germanic > West Germanic) come from different language families, so word order and morphology differ. Soniox reorders meaning in-stream instead of word by word.
Japanese is written in CJK and English in Latin, so Soniox emits correctly scripted English text.
A breakthrough in real-time Japanese to English translation
Translate before the sentence ends
English meaning lands as Japanese is spoken, not after the caption catches up.
Directional ja to en streaming
Set the source and target codes once. Both arrive in a single labeled token stream.
High quality English output
Same model across every language, including historically underserved ones.
Native-speaker Japanese STT accuracy
Accurate English translation starts with accurate Japanese recognition across accents and language switching.
Names, numbers, and domain terms
Preserved across the pair, including phone numbers, emails, and IDs.
{
"model": "stt-rt-v5",
"translation": {
"type": "one_way",
"source_language": "ja",
"target_language": "en"
}
}Japanese and English through a single stream
Japanese to English translation is built on top of Soniox Speech-to-Text API. Every spoken word is transcribed, and English translation streams mid-sentence in the same labeled token stream.
Turn it on by adding a translation block with source_language: "ja" and target_language: "en". It runs on the same WebSocket and the same model, with no extra round trip.
Live Japanese to English: written and spoken
Japanese to English speech-to-text
Translate live Japanese into written English with the Soniox STT API. Soniox streams the Japanese transcript and the English translation as speech happens.
Use it for English captions, subtitles, meeting translation, agent assist, and multilingual transcription.
Japanese to English speech-to-speech
Build full spoken Japanese to English translation by combining Soniox STT and Soniox TTS. Soniox recognizes Japanese, translates it, and speaks English with low latency.
Use it for live interpreters, bilingual voice agents, travel assistants, and customer support.
Live Japanese to English translation in action
Stream Japanese to English one-way to push all speech into English, or two-way to keep a bilingual conversation flowing between the two languages.
One-way translation
Translate live Japanese into English. Everyone in the conversation sees the same translated stream.
Ideal for live captions, multilingual meetings, broadcasts, lectures, and customer calls.
Two-way translation
Translate between Japanese and English for live bilingual conversation. Each side speaks naturally and hears the other in their own language.
Soniox supports real-time two-way translation between any two of 60+ supported languages.
Accurate on both ends of the pair
Soniox transcribes Japanese at 1.25% word error rate and English at 1.25% word error rate. Accurate recognition on both sides is what makes the translation reliable.
Speech-to-Text
Native-speaker accuracy across 60+ languages, with support for multilingual speech, alphanumerics, speaker diarization, context.
Translation
Real-time streaming translation across 3,600 language pairs, built for high quality and low delay across all supported languages.
Text-to-speech
High-fidelity speech generation in 60+ languages, built for names, alphanumerics, language switching, and ultra-low-latency streaming.
Together, they create a complete real-time low-latency speech AI platform.
About Japanese and English
Japanese has roughly 125,000,000 speakers across Japan. English has roughly 1,500,000,000 speakers across United States, United Kingdom, Canada, and Australia.
Japanese uses three writing systems simultaneously: kanji (Chinese characters), hiragana, and katakana.
English is the most widely spoken language in the world when including both native and non-native speakers.
Soniox makes Japanese to English usable in real-time translation across every supported pair.
Translate Japanese to any language
From Japanese to English, or Japanese to any of 60+ supported languages. All real-time.
Frequently asked questions
How do I translate Japanese to English with the API?
Is Japanese to English translation real-time?
What about translating English to Japanese?
Does Soniox handle CJK to Latin output?
Does Soniox handle Japanese dialects and accents?
Which other providers support Japanese to English?
How fast is Japanese to English translation?
Simple, usage-based pricing
Translate live audio from Japanese to English from ~$0.18/hour.
Translation is already built into Soniox Speech-to-Text API. When turned on, it adds about ~$0.06/hour in output token costs.
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