What is a 520 status code and how can you avoid it?

A 520 error is a Cloudflare-specific response labeled "Unknown Error" or "Web Server Returned an Unknown Error." It appears when Cloudflare successfully connects to the origin server but receives an unexpected or empty reply. This typically happens when servers are overloaded, misconfigured, or when they detect and block traffic they consider suspicious. It isn't a standard HTTP status code—it only shows up on sites protected by Cloudflare.

Why 520 errors occur

Origin servers return invalid responses when they're overwhelmed by request volume, detect bot-like behavior, have configuration issues that block Cloudflare IPs, crash or time out under load, or send empty responses to traffic that looks suspicious.

For scrapers specifically, 520s often mean your requests appear automated—missing headers, unusual request patterns, or too many requests fired too quickly. The server signals to Cloudflare that something is wrong without specifying exactly what.

How to avoid 520 errors

Send complete, realistic request headers including User-Agent, Accept, and Accept-Language. Respect rate limits by spacing requests the way a human would—a few seconds between requests. Implement retry logic with exponential backoff, since temporary overloads often clear up quickly.

Use residential proxies rather than datacenter IPs—they're far less likely to trigger anti-bot systems. Rotate user agents and headers to avoid browser fingerprinting. Watch for patterns in your error logs—a spike in 520s usually means you're tripping some protection mechanism.

The simple solution

Olostep handles Cloudflare and complex anti-bot infrastructure automatically. It manages correct headers, rate limiting, proxy rotation, and retry logic—so 520 errors don't become your problem. Built-in request handling means you receive clean data instead of error codes.

This is the advantage of modern scraping APIs. Spending days debugging 520 errors and Cloudflare protection is time wasted. Olostep resolves it automatically—let it handle anti-bot systems while you focus on using the data.

Key Takeaways

520 errors are Cloudflare-specific, signaling that the origin server returned an invalid response. They're commonly triggered by bot detection—missing headers, overly aggressive rate limiting, or suspicious request patterns. Avoid them by sending proper headers, spacing your requests, and implementing retry logic. Or use Olostep—it handles Cloudflare protection automatically, eliminating 520 errors and other anti-bot challenges so your team can focus on extracting and using data.