Japanese to English speech-to-text 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.

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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.

Real-time Japanese to English translation

Soniox streams the Japanese transcript and the English translation on the same connection, word by word, so meaning lands while the speaker is still talking.

Live Transcription

JapaneseTranscript

EnglishTranslation

One-way translation

Translate live Japanese into English. Everyone in the conversation sees the same translated stream.

YouTube

Two-way Japanese and English conversation

Each side speaks naturally and hears the other in their own language. Use it for live interpreters, bilingual voice agents, travel assistants, and customer support.

Live Conversation

Japanese

Japanese and English through a single stream

Set the source and target codes once. Transcript and translation arrive interleaved on one labeled token stream, with no extra round trip.

config.json

{
  "model": "stt-rt-v5",
  "translation": {
    "type": "one_way",
    "source_language": "ja",
    "target_language": "en"
  }
}

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.

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.

Japanese to English translation is built on top of the Soniox Speech-to-Text API. Turn it on by adding a translation block to your request.

Explore the translation docs

Estimate your Japanese to English translation cost

Set your monthly audio volume to estimate your Soniox API cost for real-time speech-to-text translation.

Pricing calculator

Stop overpaying for Japanese speech AI

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1,000 hours of audio / month

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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.

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?

Add a translation block to your real-time request with source_language "ja" and target_language "en". Soniox transcribes Japanese and streams the English translation over the same WebSocket.

Is Japanese to English translation real-time?

Yes. Soniox streams English while Japanese is still being spoken, so meaning arrives mid-sentence instead of after the sentence ends.

What about translating English to Japanese?

That direction is supported too. See the English to Japanese page, or use two-way translation to run both directions in one session.

Does Soniox handle CJK to Latin output?

Yes. Soniox outputs correctly scripted English text in Latin directly in the token stream.

Does Soniox handle Japanese dialects and accents?

Yes. Soniox handles Japanese dialects like Kanto, Kansai, and Tohoku in a single model, so English translation stays accurate across regions.

Which other providers support Japanese to English?

Based on their public docs, OpenAI, Google, Azure, and Speechmatics list both Japanese and English for real-time translation. Soniox is the only one that also supports two-way live translation across 60+ languages.

How fast is Japanese to English translation?

Soniox streams English as Japanese is being spoken, with ultra-low latency. Translation arrives before the sentence ends.

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Documentation

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See what you’ll pay

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

Pricing details