> ## Documentation Index > Fetch the complete documentation index at: https://docs.reader.dev/llms.txt > Use this file to discover all available pages before exploring further. # Scraping Engine > Playwright browser engine with proxy tier support for reliable scraping. Reader uses a single scraping engine: **Playwright** - a full headless Chrome browser connected via CDP. Chrome is spawned directly via `child_process.spawn` and Playwright connects over the Chrome DevTools Protocol. Every scrape runs through this engine, which handles JavaScript execution and anti-bot bypass via Chrome flags and the playwright-extra stealth plugin. ## Why a single engine? A browser engine handles everything a simpler HTTP client can, plus everything it can't. Sites that serve static HTML work fine in a browser. Sites that require JavaScript, handle Cloudflare challenges, or check TLS fingerprints also work - because it's a real browser. The tradeoff is speed: a plain HTTP fetch completes in \~100ms, while a browser page load takes 1-5 seconds. In practice, the reliability gain far outweighs the latency cost - failed scrapes that require retries are slower than a single browser-based scrape that succeeds on the first try. ## How a scrape runs Each scrape attempt opens a fresh tab in a warm Chrome process (the browser pool keeps Chrome running between requests): ``` 1. Open new tab in warm Chrome 2. Navigate to URL (goto → DomContentLoaded → PaintingStable) 3. Wait for optional selector (if waitForSelector is set) 4. Extract outerHTML from the rendered DOM 5. Close tab (Chrome stays alive for next request) ``` The browser is bound to a specific proxy, so all traffic from that tab routes through the configured proxy IP. ## Proxy tier selection The proxy tier used for a scrape is determined by the `proxyTier` option: * **`standard`** (datacenter proxies): fast and cheap. Works for most sites. * **`premium`** (residential proxies): uses real household IPs. Bypasses anti-bot systems that block datacenter IP ranges. If no `proxyTier` is set, Reader uses whichever proxy is configured as the default for the client. ## Quality check After the engine returns HTML, the orchestrator runs a minimal quality check: * **HTTP 2xx/3xx with any text content** → pass * **HTTP 2xx with empty body** → fail (`empty_content`) * **HTTP 4xx/5xx with empty body** → fail (`http_error`) Bot page detection (200 + block content) is handled separately by the scraper's block detection config, which is provided by the caller - Reader itself is unopinionated about what constitutes a "blocked" page. ## Where to go next How standard and premium proxies are managed. What happens when scraping fails.