Web scraping is the automated extraction of data from websites. While powerful, it requires understanding HTML structure, handling dynamic content, and respecting legal and ethical boundaries.
How Web Scraping Works
Web scrapers make HTTP requests to retrieve HTML, parse the document structure (usually with DOM or CSS selectors), extract desired data, and transform it into usable formats. Simple scrapers fetch static HTML. Advanced scrapers execute JavaScript to handle dynamic content (React, Vue, Angular apps). Scrapers must handle pagination, rate limiting, and anti-bot measures.
Static vs JavaScript-Rendered Content
Static sites return complete HTML in the initial response—easy to scrape with simple HTTP requests. JavaScript-rendered sites (SPAs) load minimal HTML then populate content via JavaScript. Scraping these requires headless browsers (Puppeteer, Playwright) to execute JavaScript and wait for content to load. APIs that support JS rendering use headless browsers internally.
Legal and Ethical Considerations
Check robots.txt before scraping—it specifies allowed/disallowed paths. Respect rate limits to avoid overwhelming servers. Some sites explicitly prohibit scraping in Terms of Service. Scraping copyrighted content or personal data may violate laws. Use official APIs when available. For public data aggregation, scraping is generally acceptable if done responsibly.