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Convert a URL to PDF in Node.js with built-in fetch

The baseline job: give the API a URL, get PDF bytes back. One POST, binary response, no callback dance — the body of the response is the file. Everything else on this page is about doing that reliably: auth, error handling, and not treating a JSON error as a PDF.

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/report/42",
    format: "pdf",
  }),
});

if (!res.ok) throw new Error(`${res.status} ${await res.text()}`);
await writeFile("page.pdf", Buffer.from(await res.arrayBuffer()));

The response is the document itself with Content-Type: application/pdf. Errors come back as JSON with an error code — which is why every sample here checks the status before writing bytes to disk: the classic integration bug in every language is saving {"error":"UNAUTHORIZED"...} as report.pdf and discovering it a week later.

PDF rendering uses the page's print stylesheet and reflows to paper width, so the width parameter does not apply to PDFs (it is a screenshot concept). If a page looks wrong as PDF, its @media print CSS is usually the culprit. Repeated identical requests inside 24 hours are served from cache — X-Cache: HIT — and not charged.

Same endpoint, one more trick: if the page you are rendering has a form on it, adding "pdf_forms": true to a PDF render brings it back with real, fillable AcroForm fields — a PDF people can type into, not a picture of one. How that works.

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-Cache`	HIT = served from the 24h cache, free.
`X-RateLimit-Remaining`	Requests left in the current second.

Full parameter reference: the docs. Hard numbers on caps and timeouts: limits.

Convert a URL to PDF in Node.js with built-in fetch

Notes for built-in fetch

Response headers worth reading

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