```yaml
product: AlterLab
title: "Headless Browser — Web Scraping Glossary | AlterLab"
comparison_context: "AlterLab is an alternative to Firecrawl, ScrapingBee, and Bright Data."
source_url: https://alterlab.io/glossary/headless-browser
```

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 browser compatibility patches applied to normalise the browser environment.

### What is Headless Browser?

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

### How does AlterLab handle Headless Browser?

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 browser compatibility patches applied to normalise the browser environment.

## Examples

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

## Related Terms

[JavaScript RenderingThe process of executing a page's JavaScript in a browser engine before extracting content, required for React, Vue, and Angular SPAs.](https://alterlab.io/glossary/javascript-rendering)[Browser FingerprintingA technique anti-bot systems use to identify bots by collecting dozens of browser attributes including Canvas, WebGL, and timing signatures.](https://alterlab.io/glossary/browser-fingerprinting)[PlaywrightAn open-source browser automation library from Microsoft that controls Chromium, Firefox, and WebKit through a unified async API.](https://alterlab.io/glossary/playwright)[PuppeteerA Node.js library providing a high-level API to control Chrome or Chromium over the DevTools Protocol, commonly used for scraping JavaScript-heavy sites.](https://alterlab.io/glossary/puppeteer)[Stealth ModeBrowser automation patches that normalise headless browser signals to match genuine user browser profiles and navigate browser environment checks.](https://alterlab.io/glossary/stealth-mode)

## Extract Headless Browser data from any website

AlterLab returns clean, structured data from any public URL — no scraper infrastructure needed. Start free, no credit card required.

[View API docs](https://alterlab.io/docs/api/rest)

[Back to Glossary](https://alterlab.io/glossary)