User-Agents, Fingerprints & Proxy Rotation
What is a user-agent and why it matters for scraping
A user-agent (UA) is a string your browser sends with every HTTP request to identify itself. It tells the server your browser name, version, operating system, and device type. Web scrapers and automation tools that send a default or missing user-agent are immediately flagged as bots. Rotating through realistic, modern user-agents is the first step to blending in with real traffic and avoiding blocks.
How websites detect bots via fingerprinting
Beyond the user-agent header, websites collect dozens of browser attributes to build a unique fingerprint: screen resolution, installed fonts, WebGL renderer, canvas hash, timezone, language, hardware concurrency, and more. Even with a perfect user-agent, an inconsistent fingerprint (e.g., a Chrome UA on Linux with an iOS screen size) triggers anti-bot systems. Advanced detection services like DataDome, PerimeterX, and Cloudflare cross-reference these signals in real time.
Common user-agent mistakes to avoid
The most frequent mistakes include: using outdated UA strings (Chrome 90 when current is 125), sending the same UA for every request, mismatching the UA with other headers (like sec-ch-ua), using headless browser signatures (HeadlessChrome), and not updating your UA pool regularly. Each of these is a clear signal to anti-bot systems. A good rotation strategy uses 50+ current UAs and matches them with consistent header sets.
Why combining UA rotation with mobile proxies works best
A perfect user-agent string is useless if the IP address behind it belongs to a datacenter. Anti-bot systems check IP reputation first. Real 4G mobile proxies from Proxy Poland use genuine LTE 4G/5G SIM cards, producing IPs that are indistinguishable from regular mobile users. Combined with proper UA rotation and fingerprint management, mobile proxies achieve near-zero detection rates on platforms like Google, Meta, Amazon, and TikTok.