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API

Japanese address ⇄ postal code, as an API.

A commercial postal code API backed by Japan Post official data, updated monthly (with a public data timestamp). Your API key is issued the moment you sign up — drop it straight into your app or service.

  • Official data, monthly sync
  • Romanized output
  • No commercial-use restrictions
  • AI-agent ready (MCP)

Start 14-day free trial Read the docs

Want to try first? The search demo and the live console in the docs work without an account.

Why

We do the tedious parts of Japanese postal data.

Japan Post publishes the raw CSV for free — but operating it is real work, especially from outside Japan. That's the part we take over.

  • Monthly official-data imports, done for you. Self-hosting means downloading and re-importing a Shift-JIS/UTF-8 CSV every month
  • Romanized address fields in every response, based on Japan Post's official romanization — no kanji handling required on your side
  • Search in kanji, kana, or romaji, with spelling-variant matching (Shimbashi/Shinbashi, Ōsaka/Osaka, Tokyo/Tōkyō)
  • Handles real-world input: block numbers and building names are stripped down to the town level automatically
  • Both directions — address → postal code and postal code → address
  • No restrictions on commercial use. Rate limits are explicit in response headers (x-ratelimit-*)
  • No origin restrictions for server-side calls; integrate in minutes

If a self-hosted CSV works for you, that's a fine choice — this API is for teams that would rather not run that pipeline.

MCP

Callable straight from AI agents.

Use address ⇄ postal code conversion as a tool from Claude, Claude Code, Cursor and other MCP clients (Model Context Protocol). Listed in the official MCP Registry.

  • Endpoint https://addresstozip.jp/mcp, authenticated with the same x-api-key
  • Tools: search_address (address → postal code) and lookup_zipcode (postal code → address)
  • Same pricing and rate limits as the regular API — no MCP surcharge

Connection details in the docs →

Pricing

Pricing

One plan. Nothing to compare.

STANDARD

14 days free, then ¥1,980 /mo

≈ $13 USD/mo — billed in Japanese yen (JPY)

  • 14-day free trial
  • Generous rate limits
  • No monthly request cap
  • Address → postal code / postal code → address
  • Romanized output (Japan Post official romanization)
  • Monthly sync with official data
  • Optional allowed-origin restriction
Start 14-day free trial

The first 14 days are free; cancel during the trial and you pay nothing. Otherwise ¥1,980/month (tax included) is charged automatically from day 15 and renews monthly. Cancel anytime from My Page. Payments are processed securely by Stripe and billed in JPY — your card issuer converts the amount to your currency. Provided best-effort, without an SLA (we say this plainly).

Enter your email
Optionally register allowed origins for browser-side use
Check out with Stripe
Credit card only. Billing and cancellation via the Stripe portal
Your API key appears on the spot
You can curl right away. Integration takes about 5 minutes

Note: the checkout and account pages are currently in Japanese. The API itself, the docs, and error messages (with lang=en) are fully usable in English — and we answer support email in English.