Error Code 520: What It Means and How to Troubleshoot It

Error code 520 is a Cloudflare response. It means the origin server sent an unexpected response. This often requires server-side checks. It may also require reviewing scraping behavior.

What is Error Code 520?

Error code 520 is a general response. It often appears when Cloudflare cannot read the origin server’s reply. Unlike a 404 Not Found response, it does not identify one precise missing resource. The origin server hosts the website you are scraping. Its unexpected response may be due to a temporary server problem. It may also be due to a configuration issue. Cloudflare cannot parse the response. Cloudflare’s 520 documentation and broader 5xx guidance explain this boundary between the proxy and the origin. During scraping, the response can interrupt a request even when the target page exists. This guide helps you troubleshoot the response in scraping projects, understand its possible causes, and apply practical fixes. MrScraper can also help with scraping workflows, and the article includes bonus tips for resolving Cloudflare error 1015. The original article was published on September 25, 2024.

Why Does it Happen During Scraping?

During scraping, this response usually points to one of two causes. Cloudflare’s 5xx error guidance covers both unexpected origin responses and protective filtering.

• Server-side problems: The target website may be experiencing technical difficulties or returning an unexpected response. There is little you can do directly in that situation beyond waiting and trying again later.
• Suspicious scraping behavior: If requests look automated, the site’s security controls may block or change them. This can cause this response.

Strategies to Avoid Error Code 520

1. Follow the target site's published rate limits so requests do not overwhelm its server. Use built-in rate limiters to keep traffic within those limits.
2. Rotate proxies where permitted to distribute requests and reduce bot-like request patterns. Advanced proxy management can simplify that rotation.
3. If a CAPTCHA appears, use an approved CAPTCHA-solving service when allowed. If not allowed, stop and follow the site's access rules. Do not try to bypass the challenge.
4. Check the target server's status before troubleshooting further, since an ongoing outage or service issue can produce these responses.
5. Adjust the time between requests and test a slower pace. This helps balance collection speed and lowers the risk of triggering defenses.
6. Use headless browsers and custom user agents when a site needs them. Configure each request to look like a real browser session. This helps reduce avoidable failures.

What We Learned

• Cloudflare Error 520 is a general response to an unexpected origin server reply. It can be caused by temporary server issues or a misconfiguration.
• During scraping, 520 errors may result from server-side issues or requests that appear automated and trigger security measures.
• Responsible scraping practices can help reduce 520 errors. Respect rate limits and adjust request intervals. Check server status and use proxies when needed.
• CAPTCHAs and other anti-bot measures may need proper handling. Tools like headless browsers and custom user agents can help with scraping.
• Ethical scraping and respect for website terms of service remain important when troubleshooting and preventing scraping errors.

Sources

Error 520 · Cloudflare Support docs

Cloudflare 5xx errors

Error responses · Cloudflare Fundamentals docs

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