post-code.info

What It Is

Postcode Info is a Japanese postal code address lookup API service designed for developers who need to automatically retrieve addresses based on postal codes in forms or internal systems. It provides a RESTful API and returns results in JSON. Typical use cases include member registration, order processing, CRM/ERP data entry, and corporate customer management.

Core Capabilities

Its core function is returning Japanese address information after inputting a 7-digit postal code or a "3桁-4桁" format postal code. The page indicates that it can return both full addresses and split addresses into fields such as prefecture, municipality, and district/block, making it convenient for frontend auto-fill or backend structured storage. A particularly valuable feature is its support for individual postal codes for large business facilities (大口事業所個別郵便番号), allowing company or facility names to be retrieved from the postal code, which is ideal for enterprise internal management systems and B2B scenarios. In terms of data, the service claims to update based on the postal code changes published monthly by Japan Post, covering municipal mergers and address changes.

API, Integration & Documentation

Integration is relatively simple: you need to apply for an API Key and pass it in the HTTP request header x-api-key. Since it uses RESTful and JSON, it can theoretically be called by any language or framework. However, the page does not list official SDKs, error codes, rate limits, complete response examples, versioning strategies, or a webhook/plugin ecosystem. Therefore, from a developer tool perspective, the basic getting-started information is clear, but the production-level documentation completeness is average.

Pricing & Reliability

The page mentions that you can create an account for free, but does not specify free tier quotas, commercial plans, overage billing, payment methods, or SLA terms. It claims to use a cloud platform and achieve an API uptime of over 99.95%, but this data is labeled as a performance record from July 2016, which has limited reference value. It is still necessary to confirm the current service status and contractual guarantees before official use.

Pros, Cons & Who It's For

Pros include a simple interface, easy JSON integration, regularly updated data, and coverage of individual postal codes for large business facilities. Cons are insufficient information disclosure, especially regarding pricing, call limits, support channels, and the lack of self-hosting and SDKs. It is suitable for e-commerce, SaaS, and enterprise information system teams whose business is primarily in Japan and who need to quickly implement postal code address auto-completion. If you require global address validation, map geocoding, or stable access from mainland China and local compliant deployment, you should evaluate alternatives such as Google Maps Geocoding API, a self-built Japan postal code database, ZipCloud, or Japan Post's open data. The page provides no basis for accessibility from China, so it is currently rated as unknown.