XRechnung CII Validator API (EN 16931)

const response = await fetch("https://api.stanzaapi.com/factur-x-validator/api/v1/validate", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "x-api-key": process.env.API_KEY || "YOUR_API_KEY"
  },
  body: JSON.stringify({
  "xml": "<?xml version=\"1.0\" encoding=\"UTF-8\"?><rsm:CrossIndustryInvoice xmlns:rsm=\"urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100\">...</rsm:CrossIndustryInvoice>"
})
});

const data = await response.json();
console.log(data);

import requests
import json

url = "https://api.stanzaapi.com/factur-x-validator/api/v1/validate"
headers = {
    "Content-Type": "application/json",
    "x-api-key": "YOUR_API_KEY"
}
payload = {
    "xml": "<?xml version=\"1.0\" encoding=\"UTF-8\"?><rsm:CrossIndustryInvoice xmlns:rsm=\"urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100\">...</rsm:CrossIndustryInvoice>"
}

response = requests.post(url, json=payload, headers=headers)
print(response.json())

package main

import (
	"bytes"
	"fmt"
	"io"
	"net/http"
	"os"
)

func main() {
	url := "https://api.stanzaapi.com/factur-x-validator/api/v1/validate"
	payload := []byte(`{"xml":"<?xml version=\"1.0\" encoding=\"UTF-8\"?><rsm:CrossIndustryInvoice xmlns:rsm=\"urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100\">...</rsm:CrossIndustryInvoice>"}`)

	req, _ := http.NewRequest("POST", url, bytes.NewBuffer(payload))
	req.Header.Add("Content-Type", "application/json")
	req.Header.Add("x-api-key", os.Getenv("API_KEY"))

	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)
	fmt.Println(string(body))
}

using System;
using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

class Program
{
    static async Task Main()
    {
        using var client = new HttpClient();
        client.DefaultRequestHeaders.Add("x-api-key", Environment.GetEnvironmentVariable("API_KEY") ?? "YOUR_API_KEY");

        var json = @"{""xml"":""<?xml version=\""1.0\"" encoding=\""UTF-8\""?><rsm:CrossIndustryInvoice xmlns:rsm=\""urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100\"">...</rsm:CrossIndustryInvoice>""}";
        var payload = new StringContent(json, Encoding.UTF8, "application/json");

        var response = await client.PostAsync("https://api.stanzaapi.com/factur-x-validator/api/v1/validate", payload);
        var content = await response.Content.ReadAsStringAsync();
        Console.WriteLine(content);
    }
}

Integrate the Stanza factur-x-validator micro-API.

Endpoint: POST https://api.stanzaapi.com/factur-x-validator/api/v1/validate
Auth header: x-api-key: YOUR_API_KEY
Content-Type: application/json
Request body:
{
  "xml": "<?xml version=\"1.0\" encoding=\"UTF-8\"?><rsm:CrossIndustryInvoice xmlns:rsm=\"urn:un:unece:uncefact:data:standard:CrossIndustryInvoice:100\">...</rsm:CrossIndustryInvoice>"
}

Rules:
- Send the request with a 2-second timeout.
- Parse the standard envelope { success, data, meta: { latency_ms, version } }.
- On failure, read { success: false, error, code } and branch on the code.
- Do not retry 4xx responses; surface the error code to the caller.
- Treat invalid-but-well-formed payloads as HTTP 200 with data.valid === false.