Turn raw Japanese into learner-ready text.

Normalize, segment, tokenize, and generate furigana or ruby HTML with one simple API built for language apps, flashcards, readers, subtitle workflows, and immersion tools.

Start building Read the API docs
No dashboard required API-key auth JSON + ruby HTML output
What it does

One practical API for Japanese text prep.

Stop stitching together one-off scripts for furigana, tokenization, sentence splitting, and display formatting. Send text in. Get app-ready output back.

正

Normalize text

Clean width differences, spacing, punctuation, and common formatting issues before your app tries to process Japanese text.

分

Segment + tokenize

Split paragraphs into sentences and return morphological tokens with surface forms, readings, and useful metadata.

読

Furigana + ruby

Generate structured furigana JSON or browser-ready ruby HTML for readers, flashcards, subtitles, and learning interfaces.

Simple pipeline

From messy text to learner-ready output.

Use only the endpoints you need, or chain them together into a clean Japanese text-prep flow.

01
Normalize

Clean width, whitespace, and punctuation.

02
Segment

Split long text into usable Japanese sentences.

03
Tokenize

Return surface forms, readings, and token metadata.

04
Furigana

Attach kana readings to kanji-containing tokens.

05
Render

Output JSON or browser-ready ruby HTML.

Developer friendly

Small API surface. Clear responses.

Designed to be boring in the best way: predictable endpoints, API-key auth, clear errors, and no account portal required.

Endpoints

All paid endpoints use the x-api-key header.

GET /health
POST /normalize
POST /segment
POST /tokenize
POST /furigana
POST /ruby-html
Example response 
{
  "tokens": [
    {
      "surface": "日本語",
      "reading": "にほんご",
      "furigana": "にほんご",
      "hasKanji": true
    },
    {
      "surface": "を",
      "reading": "を",
      "furigana": null,
      "hasKanji": false
    }
  ],
  "usage": {
    "characters": 13
  }
}
Pricing

Simple monthly plans. No surprise overages.

Hard usage caps keep costs predictable. Upgrade when you need more characters, or wait until the monthly reset.

Starter

For prototypes, flashcard tools, and small personal projects.

$12/ month
  • 500,000 characters/month
  • All text endpoints
  • JSON + ruby HTML
  • Email support
Popular

Builder

For apps, browser extensions, and heavier learning workflows.

$29/ month
  • 2,000,000 characters/month
  • All text endpoints
  • Higher practical ceiling
  • Email support

Small App

For production tools with real users but simple needs.

$79/ month
  • 10,000,000 characters/month
  • All text endpoints
  • Hard monthly cap
  • Email support

No dashboard. No overages. No account portal. Cancel through Stripe; inactive subscriptions deactivate API keys.

Built for

Language tools that need clean Japanese.

  • Reader apps that need furigana display.
  • Flashcard tools that need tokenized Japanese.
  • Browser extensions that need ruby HTML.
  • Subtitle workflows that need sentence segmentation.
  • Immersion tools that need structured text output.
Support policy

Lightweight by design.

  • Email-only support for bugs and key delivery issues.
  • No custom integration work included.
  • No formal uptime SLA.
  • No account portal or usage dashboard.
  • Clear docs and predictable API responses.
Start simple

Give your app Japanese text it can actually use.

Use JapaneseTextAPI to normalize, tokenize, segment, and render furigana without building a custom Japanese text pipeline from scratch.

Get API key View example request