5xx Server ErrorHTTP Status Code Reference

HTTP 505 HTTP Version Not Supported— What It Means, Causes & How to Fix It

The server does not support the HTTP protocol version that was used in the request. The server indicates which protocols it supports in the response.

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Common Causes

  • Client using HTTP/2 with a server that only supports HTTP/1.1
  • Very old HTTP/0.9 request to a modern server
  • Misconfigured client sending wrong protocol version

How to Fix

  1. 1Use a supported HTTP protocol version
  2. 2Update the server to support newer HTTP versions
  3. 3Check client configuration for protocol settings

Example

HTTP 505 HTTP Version Not Supported
GET /page HTTP/3

→ 505 HTTP Version Not Supported
→ Server only supports HTTP/1.1 and HTTP/2

Related Server Error Codes

500

Internal Server Error

501

Not Implemented

502

Bad Gateway

503

Service Unavailable

504

Gateway Timeout

506

Variant Also Negotiates

507

Insufficient Storage

508

Loop Detected

510

Not Extended

511

Network Authentication Required

Commonly Referenced Status Codes

The most frequently searched HTTP status codes

200OK201Created204No Content301Moved Permanently302Found400Bad Request401Unauthorized403Forbidden404Not Found422Unprocessable Content429Too Many Requests500Internal Server Error502Bad Gateway503Service Unavailable504Gateway Timeout

Related Tools

HTTP Status LookupAPI Request BuildercURL GeneratorHTTP Header ViewerHTTP Header DiffRedirect Checker