browser

Headless Browser

A web browser that runs without a graphical user interface, executing JavaScript and rendering pages exactly as a real browser would.

A headless browser is a complete web browser engine — HTML parser, CSS renderer, JavaScript engine, network stack — that operates without displaying anything on screen. It processes pages exactly as a GUI browser does, including executing JavaScript, loading external resources, setting cookies, and updating the DOM, but outputs the result programmatically rather than rendering pixels.

Headless browsers are essential for scraping modern single-page applications (SPAs) built with React, Vue, or Angular. These frameworks ship an empty HTML shell and populate all content via JavaScript after the page loads. A simple HTTP request returns nothing useful; only a browser that executes the JavaScript and waits for the DOM to populate can retrieve the real content.

Chromium and Firefox both support headless operation. The most popular automation frameworks are Playwright (multi-browser, from Microsoft) and Puppeteer (Chromium-focused, from Google). AlterLab uses headless Chromium via Playwright in Tier 4 and above for full browser rendering, with stealth patches applied to normalise the browser fingerprint.

Examples

# Enable full browser rendering
{
  "url": "https://spa-example.com",
  "render_js": true
}

Related Terms

JavaScript Rendering
The process of executing a page's JavaScript in a browser engine before extracting content, required for React, Vue, and Angular SPAs.
Browser Fingerprinting
A technique anti-bot systems use to identify bots by collecting dozens of browser attributes including Canvas, WebGL, and timing signatures.
Playwright
An open-source browser automation library from Microsoft that controls Chromium, Firefox, and WebKit through a unified async API.
Puppeteer
A Node.js library providing a high-level API to control Chrome or Chromium over the DevTools Protocol, commonly used for scraping JavaScript-heavy sites.
Stealth Mode
Browser automation patches that normalise headless browser signals to match genuine user browser profiles and evade fingerprint-based detection.
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    Headless Browser — Web Scraping Glossary | AlterLab