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Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteHTTP 520 means Cloudflare received an empty, unknown, or unexpected response from the origin server. In web scraping, seeing a 520 page tells you that the request path encountered this Cloudflare error; it does not, by itself, prove that the site blocked your scraper or that the origin server crashed. The useful next steps are to preserve the error details, identify where the response came from, and have the site operator or host correlate it with server and intermediary logs.
What HTTP 520 means for a scraper
Cloudflare describes Error 520 as occurring when the origin server returns an empty, unknown, or unexpected response to Cloudflare. The origin is the website’s server, or the upstream service that Cloudflare contacts to obtain a response. A 520 therefore describes a failure in that Cloudflare-to-origin exchange; it is not a diagnosis of why the exchange failed.
For a scraper, the response establishes that this particular request path produced a Cloudflare 520 error page. It does not establish whether the cause was the scraper, a site configuration issue, a firewall, an intermediary, or an origin application problem. Cloudflare’s possible causes include malformed or missing response data, oversized headers, origin crashes or misconfiguration, and HTTP/2 configuration problems. Treat these as investigation leads, not as proof of a bot block.
Cloudflare’s Error 520 page was last updated June 16, 2026. Its 128 KB header figure is a documented threshold associated with the error, not a measure of how common 520s are in scraping. Cloudflare says its Error Analytics are based on a 1% traffic sample, so those analytics are not a complete count of all traffic.
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Common causes to investigate
Cloudflare lists several conditions that can produce a 520. None can be confirmed from the status code alone; the error page, timestamps, request details, and logs are needed to distinguish them.
- Origin crash or misconfiguration: an application or web server may fail while handling the request. Cloudflare notes that some PHP applications can crash the origin and trigger 520 errors.
- Firewall or security software blocking Cloudflare: a firewall, security plugin, or other control may block Cloudflare IP addresses, preventing the expected exchange.
- Oversized headers: Cloudflare identifies headers exceeding 128 KB, often due to excessive cookies, as a possible cause.
- Empty or malformed response: an origin may return no usable status code or response body, or omit expected response information.
- Incorrect HTTP/2 configuration: if HTTP/2 is enabled between Cloudflare and the origin, a misconfiguration may contribute to an unexpected response.
- Authentication Origin Pull mismatch: Cloudflare identifies a case where Authentication Origin Pull is enabled at Cloudflare but the origin is not configured as expected.
- Failure in an intermediary: a load balancer, cache, proxy, or firewall between Cloudflare and the origin can be relevant even when the origin’s own logs do not show the underlying problem.
Cloudflare’s list is not a ranking. Do not change scraper headers, rotate identities, or label an event a block solely because the response code is 520; those actions may obscure the evidence without addressing the failure.
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What to collect before changing anything
Preserve enough context for the site administrator, hosting provider, or operations team to find the corresponding request. Save the complete error page if available, not just the numeric code.
- The exact resource URL, including its path and query string.
- The time of the occurrence and the timezone used by your scraper or logs.
- The Cloudflare
cf-rayvalue shown on the error page or in the response headers, if present. - The response status, response headers, and a copy or screenshot of the response body.
- The scraper’s request details, including relevant headers, cookies, redirect behavior, and whether the same request succeeds on a later attempt.
- Any request or job identifier your own system records, so the event can be matched to your logs.
Do not publish secrets while sharing a HAR file or request headers. Cookies, authorization values, and other credentials may appear in captured traffic; redact sensitive values before sending logs outside the team that is authorized to receive them.
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HTTP 520 troubleshooting sequence
- Record the error as it occurred. Preserve the URL, timestamp with timezone,
cf-rayif available, response headers, and error body. Avoid retrying repeatedly before saving this evidence. - Ask the site operator or host to correlate the event. Have them inspect origin web server logs around the recorded time for crashes, missing responses, or malformed responses. They should also check relevant load balancers, caches, proxies, and firewalls; the cause may be outside the origin server’s own logs.
- Review response size and protocol configuration. The operator should check whether headers or cookies have become excessive and verify the origin’s HTTP/2 setup if enabled. Cloudflare identifies headers over 128 KB and incorrect HTTP/2 configuration as possible causes.
- Check Cloudflare analytics and logs carefully. Cloudflare’s Logpush documentation distinguishes an
OriginResponseStatusof0when Cloudflare did not contact the origin (for example, a cache hit or revalidation) from0after a failed origin connection. Interpret it alongsideCacheStatus:hitorrevalidatedmeans no origin contact, whilemissorexpiredwith status0indicates a failed connection. A zero value alone does not mean the origin returned a 5xx response. - Escalate with the requested evidence. Cloudflare’s guidance for a 5xx support escalation asks for the full resource URL, the
cf-rayvalue, output fromhttp://<YOUR_DOMAIN>/cdn-cgi/trace, and two HAR files: one with Cloudflare enabled and one with it temporarily disabled. Cloudflare says domain owners are the customers it assists for 5xx troubleshooting, so a scraper user should pass the evidence to the site owner or administrator. - Use DNS-only or pause Cloudflare only as an owner-coordinated diagnostic. Cloudflare describes temporarily setting an affected DNS record to DNS-only or pausing Cloudflare as a workaround for diagnosis. This changes the request path; it is not a universal fix and should be done by the site owner or administrator.
How 520 differs from nearby Cloudflare errors
Related status codes describe different failure modes. The code is a useful starting point, but confirm the response page and logs before choosing a remedy. Cloudflare’s guidance for 502 and 504 also requires determining whether the origin or Cloudflare generated the response.
| Code | Cloudflare description | What to investigate |
|---|---|---|
| 520 | Origin returned an empty, unknown, or unexpected response. | Malformed or missing response data, header size, origin configuration, and relevant intermediaries. |
| 521 | Origin web server refuses connections from Cloudflare. | Origin availability and whether Cloudflare IP addresses are being blocked. |
| 522 | Cloudflare times out contacting the origin. | Connection establishment or response acknowledgement timing. |
| 502 or 504 | May be returned by the origin or by Cloudflare, depending on circumstances. | Determine which system generated the response before selecting a fix. |
Common troubleshooting mistakes
- Assuming 520 means “the scraper was blocked.” Cloudflare’s definition concerns an unexpected origin response, and its listed causes include multiple origin and configuration problems.
- Treating a retry as a fix. A later success can show that the problem was transient, but it does not identify the cause. Keep the original error’s time and identifiers for correlation.
- Reading
OriginResponseStatus: 0as an origin 5xx. CheckCacheStatusand the connection context; Cloudflare documents more than one situation in which the value can be zero. - Disabling Cloudflare without coordination. A DNS-only test changes the delivery path and may affect the site. It is a site-owner diagnostic, not a setting for a scraper user to change.
- Sending unredacted HAR files. HAR captures can contain cookies or authorization details. Remove sensitive values before sharing them with anyone who should not receive credentials.
Or skip the browser setup
If your task is to preserve a visual record of a page and its error screen, a screenshot can document what the request returned; it does not diagnose or fix a server-side 520. ScreenshotNeo is a website screenshot API and MCP server. Here is a one-request capture using cURL; replace the target URL and provide your API key:
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curl -G "https://api.screenshotneo.com/v1/shot" -d access_key=YOUR_API_KEY --data-urlencode url=https://example.com -o shot.webpSee the ScreenshotNeo API documentation for request options. ScreenshotNeo accepts cookie or consent banners as a visitor and removes more than 60 known consent platforms, newsletter popups, and chat widgets before capture; each step can be turned off. Bot checks or CAPTCHAs, blank pages, timeouts, failed loads, and cache hits are not billed, and responses indicate the page verdict and billing status. Its MCP server provides take_screenshot, get_page_info, and capture_pdf for Claude, Cursor, or another MCP client. The free plan includes 1,000 screenshots per month without a card; paid plans start at $5 for 3,000 screenshots.
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Do these 3 things before closing this tab:
1Clear out junk files and repair common Windows errors2Fix the driver behind crashes, sound loss and screen glitches3Repair Windows errors before they cause bigger problemsUsing screenshots as evidence, not as a server diagnosis
A screenshot records the visible result for a capture request. It can help an engineer see whether the response was a branded Cloudflare error page, a blank page, or other visible content, but it does not replace the status code, cf-ray, request time, or server-side logs. A screenshot also cannot establish which component generated an error when a 502 or 504 could have come from either the origin or Cloudflare.
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For incident records, keep the screenshot alongside the raw response details and the request timestamp. If you are responsible for the website, use the operator-facing Cloudflare troubleshooting steps above; if you are only scraping a third-party site, provide the collected identifiers to its administrator rather than attempting to alter its DNS or Cloudflare configuration.
Frequently Asked Questions
Does HTTP 520 always mean a website blocked my scraper?
No. Cloudflare lists several possible origin-response and configuration causes; the status code alone does not identify one.
Can a screenshot tell me which server component caused a 520?
No. It can preserve visible evidence, but identifying the cause requires request details and relevant logs.
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