UBL for JavaScript in the Browser: InvoiceXML API Examples

Browser-side JavaScript examples for creating, validating, and parsing UBL electronic invoices using the InvoiceXML API. Self-contained HTML files using vanilla JavaScript with native fetch and FormData. Compatible with modern browsers: Chrome, Firefox, Safari, Edge. No build step, no framework, no dependencies.

For background on UBL itself (what it is, the profiles, where it is used), see the main repository README.

⚠️ Security warning: API keys in browser code

API keys embedded directly in browser-side JavaScript are visible to every visitor through View Source or DevTools. Anyone can extract the key and use it against your InvoiceXML quota.

These examples are appropriate for:

• Local prototyping and testing
• Internal tools behind your company's authentication
• Single-user desktop apps wrapped in Electron or Tauri

For public-facing production websites, route requests through your own backend so the API key stays server-side. See the Node.js examples or PHP examples for server-side integration patterns.

Get your API key

Sign up and generate a key here:

→ https://www.invoicexml.com/account/authentication

Set apiKey in the examples to the raw key only, without the Bearer prefix. If your account page shows the full header value (e.g. Bearer ixml_a1b2c3...), copy only the part after Bearer . The code adds the prefix itself when building the Authorization header.

Requirements

• Any modern browser:
  • Chrome 95+
  • Firefox 90+
  • Safari 14+
  • Edge 95+
• An InvoiceXML API key
• Optional: a local web server (python -m http.server, npx serve, etc.) for testing. The examples also work by opening the .html files directly via file://.

Files in this folder

File	Operation	API endpoint
create.html	Build a UBL 2.1 XML invoice	POST /v1/create/ubl
validate.html	Validate a UBL file against the EN 16931 and Peppol rules	POST /v1/validate/ubl
extract-json.html	Parse a UBL XML into JSON	POST /v1/extract/json
ai-convert.html	(Experimental) Convert a plain PDF to UBL with AI	POST /v1/transform/to/ubl
render.html	Render UBL XML into a human-readable PDF	POST /v1/render/ubl/to/pdf

Each file is a complete, runnable HTML page. Open it in a browser, paste your API key into the <script> block, and click the button.

---

Create a UBL invoice in the browser

<button id="run">Generate invoice</button>
<script>
const payload = {
    invoice: {
        invoiceNumber: 'UBL-2026-001',
        issueDate:     '2026-05-18',
        currency:      'EUR',
        buyerReference: 'PO-2026-5571',   // Peppol requires a buyer reference
        seller: {
            name: 'Acme GmbH', vatIdentifier: 'DE123456789',
            electronicAddress: { identifier: 'DE123456789', schemeId: '9930' }, /* ... */
        },
        buyer: {
            name: 'Globex SAS',
            electronicAddress: { identifier: 'FR40303265045', schemeId: '9957' }, /* ... */
        },
        paymentDetails: { paymentAccountIdentifier: 'DE89370400440532013000' },
        lines: [{ quantity: 10, priceDetails: { netPrice: 150.00 },
                  vatInformation: { rate: 19.00 }, item: { name: 'Senior consulting' } }],
    },
    options: { profile: 'peppol-bis-3' },
};

document.getElementById('run').addEventListener('click', async () => {
    const response = await fetch('https://api.invoicexml.com/v1/create/ubl', {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
            Authorization: 'Bearer ' + apiKey,
        },
        body: JSON.stringify(payload),
    });
    const xml = await response.text();
    const blob = new Blob([xml], { type: 'application/xml' });
    const a = document.createElement('a');
    a.href = URL.createObjectURL(blob);
    a.download = 'invoice-ubl.xml';
    a.click();
});
</script>

The XML is downloaded directly to the user's machine via URL.createObjectURL and a triggered <a download>. options.profile decides the CustomizationID and the rules applied; Peppol BIS Billing 3.0 is the default.

Full example: create.html | API reference

---

Validate a UBL file in the browser

<input type="file" id="file" accept=".xml,application/xml,text/xml">
<button id="run">Validate</button>
<pre id="output"></pre>

<script>
document.getElementById('run').addEventListener('click', async () => {
    const file = document.getElementById('file').files[0];
    const form = new FormData();
    form.append('file', file);

    const response = await fetch('https://api.invoicexml.com/v1/validate/ubl', {
        method: 'POST',
        headers: { Authorization: 'Bearer ' + apiKey },
        body: form,
    });
    document.getElementById('output').textContent = await response.text();
});
</script>

The file is read directly from the <input type="file"> element. No FileReader or Blob conversion needed: FormData.append(file) accepts the File object directly.

Full example: validate.html | API reference

---

Extract UBL data as JSON in the browser

Useful for displaying invoice details in a web UI, populating form fields from an uploaded UBL file, or building drag-and-drop invoice review tools.

const form = new FormData();
form.append('file', fileInput.files[0]);

const response = await fetch('https://api.invoicexml.com/v1/extract/json', {
    method: 'POST',
    headers: { Authorization: 'Bearer ' + apiKey },
    body: form,
});
const { invoice } = await response.json();
// The invoice document sits under the "invoice" key of the response.
console.log(invoice.seller.name, invoice.totals.grandTotalAmount);

Full example: extract-json.html | API reference | Sample response

---

(Experimental) Convert a plain PDF to UBL with AI

Experimental feature. Human verification required before any production use.

AI extraction can make subtle mistakes that automated validators may not catch: wrong tax category codes, transposed amounts, missing seller VAT identifiers, incorrect currency formatting. Always review the output PDF before sending it to a customer or tax authority. See the AI conversion notes in the main README.

Full example: ai-convert.html | API reference

---

Render UBL as a readable PDF in the browser

UBL has no visual layer: the XML is the invoice, which is fine for machines and useless for the person in accounts payable who wants to read it. This endpoint renders the XML into a formatted PDF preview, auto-detecting whether the file is CII or UBL syntax. The PDF is for reading only; the XML file remains the authoritative invoice for compliance and tax purposes.

const form = new FormData();
form.append('file', fileInput.files[0]);
form.append('language', 'de');   // en, de, or fr

const response = await fetch('https://api.invoicexml.com/v1/render/ubl/to/pdf', {
    method: 'POST',
    headers: { Authorization: 'Bearer ' + apiKey },
    body: form,
});

const blob = await response.blob();
const a = document.createElement('a');
a.href = URL.createObjectURL(blob);
a.download = 'invoice-preview.pdf';
a.click();

Full example: render.html | API reference

---

Framework integration

The patterns below assume the API key is held server-side and proxied through your backend. Replace /api/ubl/... with your own proxy endpoints.

React

function CreateUblButton() {
    const [status, setStatus] = useState('');

    async function handleClick() {
        setStatus('Generating...');
        const response = await fetch('/api/ubl/create', { method: 'POST' });
        const blob = await response.blob();
        const a = document.createElement('a');
        a.href = URL.createObjectURL(blob);
        a.download = 'invoice-ubl.xml';
        a.click();
        setStatus('Done');
    }

    return <button onClick={handleClick}>Generate invoice</button>;
}

Vue 3

<template>
    <button @click="handleClick">Generate invoice</button>
    <p>{{ status }}</p>
</template>

<script setup>
import { ref } from 'vue';

const status = ref('');

async function handleClick() {
    status.value = 'Generating...';
    const response = await fetch('/api/ubl/create', { method: 'POST' });
    const blob = await response.blob();
    const a = document.createElement('a');
    a.href = URL.createObjectURL(blob);
    a.download = 'invoice-ubl.xml';
    a.click();
    status.value = 'Done';
}
</script>

Svelte

<script>
    let status = '';

    async function handleClick() {
        status = 'Generating...';
        const response = await fetch('/api/ubl/create', { method: 'POST' });
        const blob = await response.blob();
        const a = document.createElement('a');
        a.href = URL.createObjectURL(blob);
        a.download = 'invoice-ubl.xml';
        a.click();
        status = 'Done';
    }
</script>

<button on:click={handleClick}>Generate invoice</button>
<p>{status}</p>

Angular

Use HttpClient with responseType: 'blob':

this.http.post('/api/ubl/create', payload, { responseType: 'blob' })
    .subscribe(blob => {
        const a = document.createElement('a');
        a.href = URL.createObjectURL(blob);
        a.download = 'invoice-ubl.xml';
        a.click();
    });

---

Common issues

• CORS errors in the browser console: if the browser blocks the request, route through your own backend (proxy) instead of calling the API directly from the browser.
• API key visible in DevTools: this is expected when the key is embedded in client-side code. For anything beyond local prototyping, move the call to a server-side proxy.
• HTTP 401 Unauthorized: API key missing or invalid. Generate one at invoicexml.com/account/authentication. A frequent cause: setting apiKey to the whole Bearer xxx value, which sends Bearer Bearer xxx. Set the raw key only.
• HTTP 400 Bad Request on Create: a required field is missing or malformed. Frequent causes: IssueDate not in ISO format (YYYY-MM-DD), Currency not in ISO 4217 (EUR, USD), country codes not in ISO 3166-1 alpha-2 (DE, FR).
• File input always empty: fileInput.files[0] is undefined until the user actually picks a file. Always check before reading.
• Mixed content warnings: if your page is served over https://, all API calls must also be https://. The examples use https://api.invoicexml.com so this is fine, just do not change it to http://.
• file:// protocol limitations: opening the HTML directly via file:// works for these examples but breaks some browser APIs in stricter modes. Use a local server (python -m http.server, npx serve) if you hit issues.

---

Resources

• Get an InvoiceXML API key
• Create UBL API reference
• Validate UBL API reference
• Extract JSON API reference
• Extract XML API reference
• Transform to UBL API reference
• MDN: Fetch API
• MDN: FormData
• Main repository README