What is 505?
505 Status Code: HTTP Version Not Supported
The HTTP 505 HTTP Version Not Supported response status code indicates that the server does not support the HTTP protocol version that was used in the request. The server is essentially telling the client, "I don't understand the language you're speaking."
This error is relatively rare in modern web development, as most servers and clients have converged on supporting HTTP/1.1, HTTP/2, and HTTP/3. However, it can occur in certain scenarios, such as:
- Outdated Server Software: The server software might be very old and only support an older version of HTTP. In this case, upgrading the server software is usually the solution.
- Client Requesting a Newer, Unsupported Version: If a client is configured to specifically request a very new HTTP version (e.g., a future version), and the server hasn't been updated to support it, this error will occur.
- Misconfiguration: Incorrect server configuration could lead to the server rejecting valid HTTP requests based on their version.
What to do:
- Check your HTTP Version: As a client, verify the HTTP version being sent in your requests. You can typically configure this in your HTTP client library or browser settings.
- Contact the Server Administrator: If you are encountering this error consistently with a particular website or API, it's best to contact the server administrator to report the issue. They may need to update their server software or configuration.
- Try a Different Browser or Client: Sometimes, the issue is isolated to a specific browser or client library. Trying a different one can help determine if the problem lies there.
- Server-Side Issue: Understand it is almost exclusively a server-side problem and the client can do little except downgrade its HTTP version requests (if that option is available).
- Consider Network Proxies or Intermediaries: While less common, proxies or intermediary servers along the request path could be the source of the issue if they are not properly handling certain HTTP versions.
Here are links for important subjects: