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Convert an HTML form to a fillable PDF in Node.js with built-in fetch

A plain URL-to-PDF render gives you a picture of a form — nice to look at, impossible to type into. Setting "pdf_forms": true (with "format": "pdf") changes what comes back: every supported control on the page becomes a real AcroForm field at its exact rendered position, and the PDF can be filled in with Adobe Acrobat, macOS Preview, a browser viewer or a phone reader, then saved with the values kept.

Below is a complete, runnable Node.js program using built-in fetch, no third-party dependency needed. It reads your API key from the SNAPDOK_KEY environment variable — free keys take about thirty seconds and need no card.

import { writeFile } from "node:fs/promises";

const res = await fetch("https://snapdok.io/v1/render", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.SNAPDOK_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    url: "https://your-app.com/intake-form",
    format: "pdf",
    pdf_forms: true,
  }),
});

if (!res.ok) throw new Error(`${res.status} ${await res.text()}`);
await writeFile("fillable.pdf", Buffer.from(await res.arrayBuffer()));
console.log(res.headers.get("x-form-fields"), "// AcroForm fields placed");

What converts: text-like <input>s (text, email, tel, date, password, number) become text fields — password renders masked and maxlength is enforced; <textarea> becomes a multiline field; checkboxes stay checkboxes; radio inputs sharing a name become a radio group with one choice across the group; <select> becomes a dropdown. Pre-filled values, readonly and checked state carry over.

What does not: file pickers, range sliders, color pickers, hidden or invisible inputs, forms inside iframes, and fake widgets built from styled divs. These are skipped cleanly and counted in X-Form-Skipped — never guessed at, never dropped in the wrong spot.

One layout consequence worth knowing before you file a bug: the forms path measures the page at paper width with print styles — the same geometry an ordinary PDF render uses — so the width parameter has no effect here, and a mobile-first page comes out in its paper layout, not its phone layout.

Notes for built-in fetch

No dependency needed: fetch is global from Node 18 onward (snapdok's own test suite uses it). The binary-safety detail is res.arrayBuffer() → Buffer.from(...) — reaching for res.text() is the classic way to corrupt a PDF in Node. fetch does not reject on HTTP error statuses, so the res.ok check is load-bearing: without it, an expired key writes a 40-byte JSON error to disk with a .pdf extension.

Response headers worth reading

Header	Meaning
`X-Form-Fields`	How many AcroForm fields were placed.
`X-Form-Skipped`	Controls skipped (unsupported or invisible).
`X-Cache`	HIT when served from the 24h cache — not charged.

Convert an HTML form to a fillable PDF in Node.js with built-in fetch

Notes for built-in fetch

Response headers worth reading

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