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521
Cloudflare Error 521: Web server is down
Critical↻ Retryable · exponential backoffHTTP 521 Web Server Is DownNetwork
TL;DR · 10-second read
The origin actively refused the connection (TCP RST): the web server is stopped or a firewall rejects Cloudflare IPs. Start the service and allow Cloudflare ranges.
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What you see · exact log / response
Error 521 Ray ID: 8d2faf6d8e9b4a35 • 2026-10-14 22:51:30 UTC Web server is down
Fix
Being written
Copy-paste fixes for 521 are in the enrichment queue
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Last verified 2026-10-14 · Source: Cloudflare 1xxx and 5xx error reference · Official docs ↗ · ~14,800 searches/mo