Overview

Postmon is a free, open-source API for looking up Brazilian ZIP codes (CEP) and getting structured address information. Simply provide a ZIP code and receive the street name, neighborhood, city, and state — no API key required. It also supports package tracking for select Brazilian carriers.

Beginner Tip

Postmon returns HTTP 404 when a ZIP code is not found instead of an error message in the body, so check the HTTP status code first in your error handling rather than parsing the response body.

Available Data

The kind of data this API exposes, based on its documentation. We could not call the endpoint to confirm the exact field names.

IP address information
geographic location
ASN and ISP data

Example Response

Illustrative shape only — we were not able to call this endpoint (it requires credentials or exposes no public sample URL), so the fields below show the kind of data this API returns rather than a recorded response.

JSON Response · Illustrative
{
  "status": "success",
  "data": {
    "result": "Data from Postmon",
    "description": "An API to query Brazilian ZIP codes and orders easily, quickly and free",
    "timestamp": "2025-01-15T10:00:00Z"
  }
}

Field Reference

cep The queried ZIP code in 00000-000 format
logradouro Street name or address line for this ZIP code area
bairro Neighborhood or district name
cidade City name where this ZIP code is located
estado Brazilian state abbreviation (e.g., "SP", "RJ", "MG")
estado_info Additional state details including full name and area code

Implementation Example

Calls a real endpoint of this API. Replace any placeholder credentials with your own key.

Request
const url = "https://api.postmon.com.br/v1/cep/01310100";
const response = await fetch(url);
if (!response.ok) throw new Error(`Request failed: ${response.status}`);
const data = await response.json();
console.log(data);

What Can You Build?

Note: These code examples are AI-generated and unverified. Always refer to the official API documentation for accurate usage.

Common Errors & Troubleshooting

Generated guidance based on this API's documentation, not observed by us. Treat it as a starting point and check against the provider's own error reference.

404 Not Found The ZIP code (CEP) does not exist or is not in the Postmon database
Validate the CEP is 8 digits and try with and without the hyphen; some CEPs may only appear in ViaCEP or Correios databases
Connection refused or timeout Postmon is a community-maintained service with occasional downtime
Implement a fallback to ViaCEP (https://viacep.com.br) as a secondary provider for production applications
Missing address fields in response Some CEPs (particularly PO boxes or large receivers) only have partial address data
Always check for field existence before accessing; use default values for missing fields like logradouro or bairro

Metadata Score Breakdown

Estimated from metadata — endpoint not independently tested

This score is estimated from observable metadata — HTTPS support, authentication model, declared CORS, and documentation reachability — because the API requires authentication or exposes no publicly testable endpoint. The five-signal breakdown is only shown for live-tested APIs.

Metadata estimate · endpoint not independently tested

Technical Specifications

Auth No Auth
HTTPS NO
CORS UNKNOWN
Category Tracking
Difficulty Beginner
Listing details not endpoint-verified

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