diff --git a/contents/codes/520.md b/contents/codes/520.md
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+---
+# This is not a status code available in the standard, but it exists
+# with significant prominence in the wild
+set: 5
+code: 520
+title: 520 Web Server Returned an Unknown Error
+---
+
+The origin server returned an empty, unknown, or unexplained response to Cloudflare.[1]
+
+---
+
+* Source: [unknown?][1]
+
+[1]: <https://support.cloudflare.com/hc/en-us/articles/115003011431#520error>
diff --git a/contents/codes/521.md b/contents/codes/521.md
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+---
+# This is not a status code available in the standard, but it exists
+# with significant prominence in the wild
+set: 5
+code: 521
+title: Web Server Is Down
+---
+
+This status code is not specified in any RFCs, but is used by CloudFlare's reverse proxies to indicate that the origin webserver refused the connection.[1]
+
+---
+
+* Source: [unknown?][1]
+
+[1]: <https://support.cloudflare.com/hc/en-us/articles/115003011431#521error>
diff --git a/contents/codes/522.md b/contents/codes/522.md
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+---
+# This is not a status code available in the standard, but it exists
+# with significant prominence in the wild
+set: 5
+code: 522
+title: Connection Timed Out
+---
+
+Cloudflare could not negotiate a TCP handshake with the origin server.[1]
+
+---
+
+* Source: [unknown?][1]
+
+[1]: <https://support.cloudflare.com/hc/en-us/articles/115003011431#522error>
diff --git a/contents/codes/523.md b/contents/codes/523.md
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+---
+# This is not a status code available in the standard, but it exists
+# with significant prominence in the wild
+set: 5
+code: 523
+title: Origin Is Unreachable
+---
+
+Cloudflare could not reach the origin server; for example, if the DNS records for the origin server are incorrect.[1]
+
+---
+
+* Source: [unknown?][1]
+
+[1]: <https://support.cloudflare.com/hc/en-us/articles/115003011431#523error>
diff --git a/contents/codes/524.md b/contents/codes/524.md
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+++ b/contents/codes/524.md
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+---
+# This is not a status code available in the standard, but it exists
+# with significant prominence in the wild
+set: 5
+code: 524
+title: Origin Is Unreachable
+---
+
+Cloudflare was able to complete a TCP connection to the origin server, but did not receive a timely HTTP response.[1]
+
+---
+
+* Source: [unknown?][1]
+
+[1]: <https://support.cloudflare.com/hc/en-us/articles/115003011431#524error>
diff --git a/contents/codes/525.md b/contents/codes/525.md
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+++ b/contents/codes/525.md
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+---
+# This is not a status code available in the standard, but it exists
+# with significant prominence in the wild
+set: 5
+code: 525
+title: Origin Is Unreachable
+---
+
+Cloudflare could not negotiate a SSL/TLS handshake with the origin server.[1]
+
+---
+
+* Source: [unknown?][1]
+
+[1]: <https://support.cloudflare.com/hc/en-us/articles/115003011431#525error>
diff --git a/contents/codes/526.md b/contents/codes/526.md
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+++ b/contents/codes/526.md
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+---
+# This is not a status code available in the standard, but it exists
+# with significant prominence in the wild
+set: 5
+code: 526
+title: Origin Is Unreachable
+---
+
+Cloudflare could not validate the SSL certificate on the origin web server.[1]
+
+---
+
+* Source: [unknown?][1]
+
+[1]: <https://support.cloudflare.com/hc/en-us/articles/115003011431#526error>