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Deploy a Browser Rendering Worker

By following this guide, you will create a Worker that uses the Browser Rendering API to take screenshots from web pages. This is a common use case for browser automation.

  1. Sign up for a Cloudflare account ↗.
  2. Install npm ↗.
  3. Install Node.js ↗.

Node.js version manager

Use a Node version manager like Volta ↗ or nvm ↗ to avoid permission issues and change Node.js versions. Wrangler, discussed later in this guide, requires a Node version of 16.17.0 or later.

1. Create a Worker project

Cloudflare Workers provides a serverless execution environment that allows you to create new applications or augment existing ones without configuring or maintaining infrastructure. Your Worker application is a container to interact with a headless browser to do actions, such as taking screenshots.

Create a new Worker project named browser-worker by running:

Terminal window
npm create cloudflare@latest -- browser-worker

For setup, select the following options:

  • For What would you like to start with?, choose Hello World example.
  • For Which template would you like to use?, choose Hello World Worker.
  • For Which language do you want to use?, choose JavaScript / Typescript.
  • For Do you want to use git for version control?, choose Yes.
  • For Do you want to deploy your application?, choose No (we will be making some changes before deploying).

2. Install Puppeteer

In your browser-worker directory, install Cloudflare’s fork of Puppeteer:

Terminal window
npm install @cloudflare/puppeteer --save-dev

3. Create a KV namespace

Browser Rendering can be used with other developer products. You might need a relational database, an R2 bucket to archive your crawled pages and assets, a Durable Object to keep your browser instance alive and share it with multiple requests, or Queues to handle your jobs asynchronous.

For the purpose of this guide, you are going to use a KV store to cache your screenshots.

Create two namespaces, one for production, and one for development.

Terminal window
npx wrangler kv:namespace create BROWSER_KV_DEMO
npx wrangler kv:namespace create BROWSER_KV_DEMO --preview

Take note of the IDs for the next step.

4. Configure wrangler.toml

Configure your browser-worker project’s wrangler.toml file by adding a browser binding and a Node.js compatibility flag. Bindings allow your Workers to interact with resources on the Cloudflare developer platform. Your browser binding name is set by you, this guide uses the name MYBROWSER. Browser bindings allow for communication between a Worker and a headless browser which allows you to do actions such as taking a screenshot, generating a PDF and more.

Update your wrangler.toml configuration file with the Browser Rendering API binding and the KV namespaces you created:

name = "browser-worker"
main = "src/index.js"
compatibility_date = "2023-03-14"
compatibility_flags = [ "nodejs_compat" ]


browser = { binding = "MYBROWSER" }
kv_namespaces = [
  { binding = "BROWSER_KV_DEMO", id = "22cf855786094a88a6906f8edac425cd", preview_id = "e1f8b68b68d24381b57071445f96e623" }
]

5. Code

Update src/index.js with your Worker code:

import puppeteer from "@cloudflare/puppeteer";


export default {
  async fetch(request, env) {
    const { searchParams } = new URL(request.url);
    let url = searchParams.get("url");
    let img;
    if (url) {
      url = new URL(url).toString(); // normalize
      img = await env.BROWSER_KV_DEMO.get(url, { type: "arrayBuffer" });
      if (img === null) {
        const browser = await puppeteer.launch(env.MYBROWSER);
        const page = await browser.newPage();
        await page.goto(url);
        img = await page.screenshot();
        await env.BROWSER_KV_DEMO.put(url, img, {
          expirationTtl: 60 * 60 * 24,
        });
        await browser.close();
      }
      return new Response(img, {
        headers: {
          "content-type": "image/jpeg",
        },
      });
    } else {
      return new Response("Please add an ?url=https://example.com/ parameter");
    }
  },
};

This Worker instantiates a browser using Puppeteer, opens a new page, navigates to what you put in the "url" parameter, takes a screenshot of the page, stores the screenshot in KV, closes the browser, and responds with the JPEG image of the screenshot.

If your Worker is running in production, it will store the screenshot to the production KV namespace. If you are running wrangler dev, it will store the screenshot to the dev KV namespace.

If the same "url" is requested again, it will use the cached version in KV instead, unless it expired.

6. Test

Run npx wrangler dev --remote to test your Worker remotely before deploying to Cloudflare’s global network. Local mode support does not exist for Browser Rendering so --remote is required.

To test taking your first screenshot, go to the following URL:

<LOCAL_HOST_URL>/?url=https://example.com

7. Deploy

Run npx wrangler deploy to deploy your Worker to the Cloudflare global network.

To take your first screenshot, go to the following URL:

<YOUR_WORKER>.<YOUR_SUBDOMAIN>.workers.dev/?url=https://example.com

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