Introduction

Your Web server thinks that the HTTP data stream sent by the client (e.g. your Web browser or our CheckUpDown robot) identifies a URL resource whose actual media type 1) does not agree with the media type specified on the request or 2) is incompatible with the current data for the resource or 3) is incompatible with the HTTP method specified on the request.

Detecting exactly what is causing this problem can be difficult, because there a number of possible reasons. Often the request involves transfer of data from the client to the Web server (e.g. a file upload via the PUT method), in which case you need to confirm with your ISP which media types are acceptable for upload.

415 errors in the HTTP cycle

Any client (e.g. your Web browser or our CheckUpDown robot) goes through the following cycle:

• Obtain an IP address from the IP name of your site (your site URL without the leading 'http://'). This lookup (conversion of IP name to IP address) is provided by domain name servers (DNSs).
• Open an IP socket connection to that IP address.
• Write an HTTP data stream through that socket.
• Receive an HTTP data stream back from your Web server in response. This data stream contains status codes whose values are determined by the HTTP protocol. Parse this data stream for status codes and other useful information.

This error occurs in the final step above when the client receive ans HTTP status code that it recognises as '415'.

Resolving 415 errors - general

This error seldom occurs in most Web traffic, particularly when the client system is a Web browser.

If your client system is not a Web browser, the problem can only be resolved by examining what the client is trying to do then discussing with your ISP why the Web server rejects the media type specified by the client system.

Resolving 415 errors - CheckUpDown

This error should simply never occur on your CheckUpDown account. If it does, it typically indicates defective programming of our systems or of the Web server which manages your site. The content of the HTTP data stream we send is plain text, and the HTTP data stream we expect back is a simple byte stream. Both data streams make no reference to any specific medium.

Please contact us (email preferred) whenever you encounter 415 errors - there is nothing you can do to sort them out. We then have to liaise with your ISP and the vendor of your Web server software to agree the exact reason for the error.