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Take a full-page screenshot in Node.js with built-in fetch

"full_page": true captures the whole document, not just the viewport — the render scrolls the page, waits for lazy-loaded images along the way, and returns one tall image. width sets the viewport width the page lays itself out at; height is measured, not guessed.

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: "png",
    full_page: true,
    width: 1280,
  }),
});

if (!res.ok) throw new Error(`${res.status} ${await res.text()}`);
await writeFile("full.png", Buffer.from(await res.arrayBuffer()));
console.log(res.headers.get("x-page-height"), "// measured document height in CSS px");

Very tall pages hit a documented cap rather than an out-of-memory surprise: images are cut off at 20,000 CSS px, and the response says so explicitly — X-Full-Page-Truncated: 1 plus X-Page-Height with the real document height. If you need everything past the cap, ask for "tile": true and the render returns a ZIP of overlapping numbered tiles instead (covered in its own guide, linked below).

Sticky headers are the classic full-page artifact — a bar designed to follow the viewport can repeat down a scrolled capture. If a page renders oddly, try "wait_until": "networkidle" first so animations and late images settle before the scroll pass.

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

HeaderMeaning
X-Page-HeightFull document height in CSS px.
X-Full-Page-Truncated1 when the image stops at the 20,000 px cap.
X-Full-Page-Max-HeightThe cap itself.

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

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