CPFHub.io
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Look up a CPF with .NET / C#

Look up a CPF (Brazil's individual taxpayer ID) with .NET using the native HttpClient. No external packages, .NET 6+.

Using Cursor, Lovable, v0 or another AI? Copy the Simple Lookup prompt and paste it into your assistant.

Open in Cursor

Before you start

  1. Create a free account at app.cpfhub.io: the Free plan includes 50 credits and does not ask for a card.
  2. Copy your API key from app.cpfhub.io/api-keys.
  3. Store the key in an environment variable, never in your code:
bash
export CPFHUB_API_KEY="your_api_key"

Example

C#
using System.Net;
using System.Net.Http.Json;
using System.Text.Json;

var cpf = "12345678909";

using var client = new HttpClient { Timeout = TimeSpan.FromSeconds(10) };
client.DefaultRequestHeaders.Add("x-api-key", Environment.GetEnvironmentVariable("CPFHUB_API_KEY"));

using var response = await client.GetAsync($"https://api.cpfhub.io/cpf/{cpf}");
var body = await response.Content.ReadFromJsonAsync<JsonElement>();

switch (response.StatusCode)
{
    case HttpStatusCode.OK:
        var data = body.GetProperty("data");
        Console.WriteLine($"{data.GetProperty("name")} {data.GetProperty("birthDate")}");
        break;
    case HttpStatusCode.NotFound:
        Console.WriteLine("CPF not found (no credit charged)");
        break;
    default:
        // error comes as text ("...") or as an object ({"message": "..."})
        var err = body.GetProperty("error");
        var message = err.ValueKind == JsonValueKind.Object
            ? err.GetProperty("message").GetString()
            : err.GetString();
        throw new Exception($"Error {(int)response.StatusCode}: {message}");
}

Paste it into the Program.cs of a console project (dotnet new console) and run it with dotnet run.

Response

Found CPF (200, uses 1 credit):

JSON
{
  "success": true,
  "data": {
    "cpf": "12345678909",
    "name": "Fulano de Tal",
    "nameUpper": "FULANO DE TAL",
    "gender": "M",
    "birthDate": "15/06/1990",
    "day": 15,
    "month": 6,
    "year": 1990
  }
}

CPF not found (404, does not use a credit):

JSON
{
  "success": false,
  "data": null,
  "error": { "message": "CPF não encontrado na base de dados" }
}

The CPF 12345678909 is fictional, used only in the examples. gender can be null. The error.message text comes from the API in Portuguese ("CPF not found in the database").

Errors

StatusWhat it meansWhat to do
404CPF is not in the databaseTreat it as "not found". Does not use a credit.
400 / 422CPF does not have 11 digits or has an invalid check digitFix the input. Does not use a credit.
401Missing or invalid API keyCheck the CPFHUB_API_KEY variable.
403Credits used up or inactive accountCheck your balance with GET /quota or top up in the dashboard.
429Per-minute request limitWait the number of seconds in the Retry-After header and try again.
5xxTemporary failureTry again after a few seconds.

The error field can be text ("error": "...") or an object ("error": { "message": "..." }), depending on the status. The examples above handle both formats. Full list in Error Codes.

Next steps