505 HTTP Version Not Supported

What it means

Rare with modern clients; usually a misconfigured client or proxy.

Common causes

• A client using an outdated or unsupported HTTP version.

How to fix it

1. Update the client or proxy to use HTTP/1.1 or HTTP/2.

Example response

HTTP/1.1 505 HTTP Version Not Supported
Content-Type: text/plain; charset=utf-8

Worked example

A gateway or server cannot complete an otherwise valid request. Check the origin service and proxy logs, correct the server-side cause, then retry after the service is healthy.

How to read this response

1. Find the status line in your browser's Network panel, API client, or server access log.
2. Read the response body and headers shown above; headers such as Location, Allow, Retry-After, and WWW-Authenticate explain the next step.
3. Use the code's class to orient your diagnosis: informational, successful, redirected, request-related, or server-side.

How to check a status code

Enter a URL in the HTTP Status Checker to see its status code, every redirect hop, and response time. For redirect-heavy pages, the Website Speed Test shows how much time redirects add.

Frequently asked questions

What it means: HTTP 505

505 HTTP Version Not Supported: The server does not support the HTTP version used in the request.

Common causes: 505

A client using an outdated or unsupported HTTP version.

How to fix it: HTTP 505

Update the client or proxy to use HTTP/1.1 or HTTP/2.

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