English to Japanese speech-to-text translation API

Stream English (English) speech and get Japanese (日本語) back in real time. One WebSocket, ISO codes en to ja, and ultra-low latency for voice agents and live apps.

Build with API

You speak one language — we instantly translate to another.

Trusted by teams building global voice products

Production-ready English to Japanese translation API

Real English speech includes accents, regional dialects, code switching, and domain-specific vocabulary. Soniox recognizes it in a single model and streams Japanese while the speaker is still talking.

English (Indo-European > Germanic > West Germanic) and Japanese (Japonic) come from different language families, so word order and morphology differ. Soniox reorders meaning in-stream instead of word by word.

English is written in Latin and Japanese in CJK, so Soniox emits correctly scripted Japanese text.

Real-time English to Japanese translation

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

Live Transcription

EnglishTranscript

JapaneseTranslation

One-way translation

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

YouTube

Two-way English and Japanese 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

English

English and Japanese 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": "en",
    "target_language": "ja"
  }
}

A breakthrough in real-time English to Japanese translation

Translate before the sentence ends

Japanese meaning lands as English is spoken, not after the caption catches up.

Directional en to ja streaming

Set the source and target codes once. Both arrive in a single labeled token stream.

Native-speaker English STT accuracy

Accurate Japanese translation starts with accurate English recognition across accents and language switching.

Names, numbers, and domain terms

Preserved across the pair, including phone numbers, emails, and IDs.

English to Japanese 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 English to Japanese 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 English 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.

Translate English to any language

From English to Japanese, or English to any of 60+ supported languages. All real-time.

Frequently asked questions

How do I translate English to Japanese with the API?

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

Is English to Japanese translation real-time?

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

What about translating Japanese to English?

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

Does Soniox handle Latin to CJK output?

Yes. Soniox outputs correctly scripted Japanese text in CJK directly in the token stream.

Does Soniox handle English dialects and accents?

Yes. Soniox handles English dialects like American English, British English, and Australian English in a single model, so Japanese translation stays accurate across regions.

Which other providers support English to Japanese?

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

How fast is English to Japanese translation?

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

Ready to get started?

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, 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