No signup · Free · Unlimited · MIT

Every Japanese zipcode
served from a CDN

A Japan zipcode dataset for indie developers and OSS. 120,680 normalized entries are delivered from Cloudflare Pages, and each language SDK lets you take them all the way offline.

120,680
Zipcodes
948
3-digit prefixes
10 files
1-digit groups
¥0
Forever
Playground

Type 7 digits
A real CDN answers

The form below hits jpzip.nadai.dev directly from your browser. If CORS clears you get real data; otherwise a built-in demo response.

QUERY
EXAMPLES
endpoint: https://jpzip.nadai.dev/p/{prefix}.json
cache: L1 memory · 24h CDN
待機中GET /p/—.json
左に郵便番号を入れて
「検索」を押してみよう
SDK

A 3-line SDK
Same signature every language

The protocol is fixed, so each SDK is just a few dozen lines — with identical signatures across languages.

~30 LoC
import { lookup, preload } from "@jpzip/jpzip"

// 単発検索 — /p/231.json を fetch して結果を抽出
const entry = await lookup("2310017")
// → { prefecture: "神奈川県", city: "横浜市中区",
//     towns: [{ town: "本町", kana: "ホンチョウ" }], ... }

// オフライン化 — 全件を SDK 内にキャッシュ
await preload({ scope: "all" })

// 以降の lookup() はネットワーク不要
const e2 = await lookup("1500001")
{ "prefecture": "神奈川県", "city": "横浜市中区", "towns": [{ "town": "本町" }] }
Why jpzip

Free by design
Hard to break

No Workers, no R2, no KV. Even at billions of requests, there is no metered axis to bill.

¥

Free forever

Runs entirely on Cloudflare Pages free tier. ~1,000 files, each under 25 MiB — there is simply no metered axis to bill.

Offline-ready

preload({ scope: "all" }) caches the full dataset into the SDK. After that, every lookup works without network.

A

No signup, no auth

No API key needed. CORS allows all origins. Fetch directly from the browser.

Monthly auto-updates

GitHub Actions ingests the latest Japan Post data on the 1st and 15th of each month and redeploys the CDN.

Kanji, kana, romaji

KEN_ALL and KEN_ALL_ROME are pre-joined. The MIC municipality code (city_code) is included too.

MIT & Public Domain

SDKs are MIT. The data is effectively public domain (Japan Post). Commercial use and redistribution are free.

Three lines one zipcode lookup

No signup, no API key, no billing surprises. Install from npm (or your language’s package manager) and run it in the browser, on a server, or at the edge.