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[Fundamentals, Support] Update header limits #25872

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merged 3 commits into from
Oct 16, 2025
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[Fundamentals, Support] Update header limits #25872

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3fdfe80
Update connection-limits.mdx
mbullock1986 Oct 16, 2025
c0a5fe7
Update unit
pedrosousa Oct 16, 2025
16c0d83
Update "Error 520" page
pedrosousa Oct 16, 2025
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4 changes: 2 additions & 2 deletions src/content/docs/fundamentals/reference/connection-limits.mdx
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Expand Up @@ -45,11 +45,11 @@ Ensure HTTP keep-alive connections are enabled on your origin. Cloudflare reuses

## Request limits

URLs have a limit of 16 KB. Request headers have a total limit of 32 KB, but each header is limited to 16 KB.
URLs have a limit of 16 KB. Request headers have a total limit of 128 KB.

## Response limits

Response headers observe a total limit of 32 KB, but each header is limited to 16 KB.
Response headers observe a total limit of 128 KB.

## Cache limits

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3 changes: 1 addition & 2 deletions ...s/support/troubleshooting/http-status-codes/cloudflare-5xx-errors/error-520.mdx
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Expand Up @@ -14,7 +14,7 @@ This error is often triggered by:

- Origin server crashes or misconfigurations.
- Firewalls or security plugins blocking [Cloudflare IPs](https://www.cloudflare.com/ips) at your origin.
- Headers exceeding 16 KB (often due to excessive cookies).
- Headers exceeding 128 KB (often due to excessive cookies).
- Empty or malformed responses lacking an HTTP status code or response body.
- Missing response headers or origin web server not returning [proper HTTP error responses](https://www.iana.org/assignments/http-status-codes/http-status-codes.xhtml).
- Incorrect HTTP/2 configuration at the origin server.
Expand All @@ -38,7 +38,6 @@ As a temporary workaround, you can set the affected DNS record to [DNS-only](/dn
- If HTTP/2 is enabled at your origin server, ensure it is correctly set up. Cloudflare connects to servers who announce support of HTTP/2 connections via [ALPN](https://blog.cloudflare.com/introducing-http2). If the origin web server accepts the HTTP/2 connection but then does not respect or support the protocol, an HTTP `520` error will be returned. You can disable the [HTTP/2 to Origin](/speed/optimization/protocol/http2-to-origin/#disable-http2-to-origin) in **Speed** > **Optimization** > **Protocol Optimization** on the Cloudflare dashboard.

- If `520` errors continue after contacting your hosting provider or site administrator, provide the following information to [Cloudflare Support](/support/contacting-cloudflare-support/):

- Full URL(s) of the resource requested when the error occurred.
- Cloudflare **cf-ray** from the `520` error message.
- Output from `http://<YOUR_DOMAIN>/cdn-cgi/trace`.
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