---
title: "521 Web Server Is Down in Cloudflare"
canonical: "https://lemwatch.com/http-status-codes/521/in-cloudflare"
platform: "Cloudflare"
last_verified: "2026-08-11"
source: "https://lemwatch.com"
---

# HTTP 521 Web Server Is Down in Cloudflare

**Platform** — Cloudflare — CDN, WAF, and edge network in front of your origin.

**Where it surfaces** — The Cloudflare edge before your origin ever sees the request. Look at the Ray ID in the response.

## Cause on this platform

Origin server refused the Cloudflare edge connection — often a firewall blocking Cloudflare IPs.

## Fix on this platform

Whitelist Cloudflare's IP ranges at the origin firewall (see cloudflare.com/ips).


## Generic reference

The origin web server has refused or is not responding to Cloudflare's connection.

_Canonical HTML page: https://lemwatch.com/http-status-codes/521/in-cloudflare_