Why Cloudflare Breaks Proxy-Only Scrapers
Cloudflare can prevent proxy-only scrapers from accessing content, even when these scrapers employ residential proxies and set a Chrome user agent. Scrapers often encounter a 403 HTTP status code or a 200 status code that delivers a Cloudflare challenge page, such as "Just a moment...", cf-chl, or turnstile, rather than the intended product, article, or search result. This behavior indicates that the site is not solely blocking IP addresses. The issue arises because a proxy alters the origin of the request but does not replicate the full behavior of a Chrome HTTP client. An example using the `requests` Python library demonstrates this, setting a `User-Agent` header to "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/121.0.0.0 Safari/537.36" and configuring proxies. The `requests.get` call might return a 403 status or a 200 status with a body containing a Cloudflare challenge. A consequence is that scrapers designed to only check the HTTP status code may mistakenly process a block page as a successful data retrieval.
Developers building scrapers face challenges from Cloudflare's blocking mechanisms, which can lead to failed data collection or misinterpretation of scrape results.