Member Avatar for jessica1410

Guys i heard 301 Error and 404 Error but can anyone know that "what is 505 Error?"

please share your answers with me... i want to know about this Error in deeply.

Thank You.

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Brief, practical explanation and troubleshooting steps (building on , and ).

A 505-style response means the server refused to handle the HTTP protocol version indicated by the incoming request. That refusal usually comes from the origin server or an intermediary (reverse proxy, load balancer, CDN) that doesn't understand or accept the negotiated protocol. The formal definition and semantics are documented in the HTTP specs and browser docs (RFC 7231 section 6.6.6, MDN: 505).

Common causes and where to look

  • Protocol mismatch: client requests HTTP/2 but the path to origin only speaks HTTP/1.x, or vice versa.
  • Intermediary bugs or misconfiguration: reverse proxies or CDNs that fail during protocol negotiation.
  • Malformed request lines or non-HTTP traffic hitting an HTTP port.
  • App-server connectors (e.g., old Java connectors) that don’t support newer protocol features.
    Check server and proxy logs (timestamps, client IP, request line), and test direct connections to the origin (bypass CDN) to narrow where the 505 is generated.

Quick reproducible checks

  • Force different versions with curl to see what the server accepts:
    curl -I --http1.1 -v https://example.com
curl -I --http2 -v https://example.com
  • Use browser DevTools “Protocol”/“Protocol Version” column to see negotiated protocol.
  • Reproduce the request directly against each hop (origin, load balancer, CDN) to find the failing component.

Mitigation and SEO note

  • Short-term: configure the gateway to downgrade/translate protocols or force clients to use an accepted version.
  • Long-term: update server/proxy software to support modern HTTP versions and enable proper TLS/ALPN negotiation.
  • For search engines, any persistent 5xx (including 505) can reduce crawling and indexing; monitor Search Console and fix repeated server-side failures ().

If the error is intermittent as observed, focus on transient elements (load balancers, autoscaling nodes, or partial config rollouts).

Recommended Answers

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Member Avatar for Tiggerito

I googled it:

505 Error = HTTP version not supported

What I think that means is it does not accept your browser. Either upgrade or switch.

I may be wrong.

Member Avatar for motik

Error Message: Error 501/505: Not Implemented or Not Supported

Member Avatar for Bella Ross

Guys i heard 301 Error and 404 Error but can anyone know that "what is 505 Error?"

please share your answers with me... i want to know about this Error in deeply.

Thank You.

After testing it for long sometimes it has issues showing 505 error

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