In the world of programming, we often encounter scenarios where we need to convert the contents of a webpage into a PDF document. This is particularly common when we want to include a snapshot of the web content in emails, reports, or offline documentation. One challenge faced during this process is ensuring that the webpage is fully loaded before conversion. This post will guide you through some ways to achieve this task programmatically.

an infographic of a webpage being turned into a pdf

1. Using Python with pdfkit and wkhtmltopdf

pdfkit is a Python wrapper for wkhtmltopdf, which converts HTML to PDF using Webkit, the browser engine behind Chrome and Safari. You’ll need to install both libraries to use them:

pip install pdfkit

For wkhtmltopdf, follow the installation instructions provided on the official website.

After installing, you can use the following Python script to convert a webpage to a PDF:

import pdfkit

pdfkit.from_url('http://example.com', 'out.pdf')

2. Using Node.js with Puppeteer

Puppeteer is a Node library which provides a high-level API to control Chrome or Chromium over the DevTools Protocol. Puppeteer runs headless by default but can be configured to run full (non-headless) Chrome or Chromium. Here’s a simple example:

First, install Puppeteer:

npm i puppeteer

Then, use this script to convert a webpage to a PDF:

const puppeteer = require("puppeteer");

async function run() {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto("http://example.com", { waitUntil: "networkidle2" });
  await page.pdf({ path: "out.pdf", format: "A4" });

  await browser.close();
}

run();

3. Handling The Challenge of Fully Loading a Page

As mentioned earlier, a common challenge when converting a webpage to a PDF is making sure the page is fully loaded. This is especially important for websites that use JavaScript to load content dynamically.

Both the Python and Node.js examples above offer ways to deal with this issue:

  • Python: pdfkit automatically waits for the entire webpage to load before creating the PDF.
  • Node.js: In the Puppeteer script, we use the {waitUntil: 'networkidle2'} option in page.goto(). This option tells Puppeteer to consider navigation to be finished when there are no more than 2 network connections for at least 500 ms.

4. Using CSS Selectors to Ensure Page Readiness

In some cases, merely waiting for the network to settle might not be enough to ensure that the page is fully loaded, especially if the page contains complex JavaScript or dynamically loaded content. This is where CSS selectors come in handy.

With Puppeteer, you can use the page.waitForSelector() function to wait for a specific element, identified by a CSS selector, to appear on the page before proceeding. Here’s how you can modify the previous script to wait for a specific element:

const puppeteer = require("puppeteer");

async function run() {
  const browser = await puppeteer.launch();
  const page = await browser.newPage();
  await page.goto("http://example.com", { waitUntil: "networkidle2" });
  // Wait for the element identified by the CSS selector ".my-element" to load
  await page.waitForSelector(".my-element");
  await page.pdf({ path: "out.pdf", format: "A4" });

  await browser.close();
}

run();

By using this strategy, you can ensure that the most critical parts of the webpage are loaded before converting the page to a PDF. This can be particularly useful for pages that load different parts of their content at different times, or for scenarios where you only need a specific part of the page to be loaded.

I hope this helps! Let me know if you have any further questions.