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How to generate a PDF from a template in Node.js

Most documents are one layout rendered against changing data: the same invoice for a thousand customers, the same certificate for every course completion. The /v1/generate/template endpoint separates those concerns — you POST a Jinja2 template plus a JSON data object, and Inkspan renders the template and converts the result to PDF in one request.

Keeping the template in the request rather than in your codebase means non-engineers can change document layout without a deploy, and you can store templates in your own database per tenant.

Also in: cURL · Python

Node.js example

import fs from 'node:fs';

const res = await fetch('https://api.inkspan.dev/v1/generate/template', {
  method: 'POST',
  headers: {
    'X-API-Key': process.env.INKSPAN_KEY,
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
    "template": "<h1>Invoice {{ number }}</h1>{% for i in items %}<p>{{ i.desc }}: ${{ i.amt }}</p>{% endfor %}<h3>Total: ${{ total }}</h3>",
    "data": {
      "number": "INV-1042",
      "items": [
        {
          "desc": "Pro Plan",
          "amt": 49
        }
      ],
      "total": 49
    }
  }),
});
if (!res.ok) throw new Error(await res.text());
fs.writeFileSync('document.pdf', Buffer.from(await res.arrayBuffer()));

Request parameters

Response

Returns a PDF as a binary stream with Content-Type: application/pdf and Content-Disposition: attachment; filename=document.pdf. Write the response body straight to disk — do not parse it as JSON.

Things that catch people out

• Template syntax is Jinja2, not Handlebars or Mustache. Loops are {% for i in items %}…{% endfor %}, not {{#each}}.
• Only top-level keys in data become variables. Passing {"data": {"invoice": {...}}} means you reference {{ invoice.number }}, not {{ number }}.
• Undefined variables render as empty rather than raising. Validate your data server-side if a missing field should be an error.
• Escape user-supplied values with the |e filter if they may contain HTML, or they will be interpreted as markup.

Errors

Failed requests do not count against your quota; only successful ones are metered.

Frequently asked questions

Can I reuse a stored template?

Templates are sent per request, so store yours in your own database or object storage and send it with each call. This keeps tenant-specific layouts under your control.

Do Jinja2 filters work?

Yes — standard filters such as |round, |upper, and |default are available for formatting values inside the template.

How do I format currency?

Format on your side before sending, or use a filter in the template. Sending pre-formatted strings is the more predictable option for money.

Related Generate guides: generate a PDF from HTML · convert Markdown to PDF