Gary Illyes from Google posted information on how Google Search handles the 103 early hints HTTP server status response. He said, “Googlebot will ignore the 103 and wait for the subsequent response.”

This was posted on LinkedIn and wrote, “HTTP 103 should be handled gracefully by Googlebot. If the response from the server is formatted as described in the experimental standard, Googlebot will ignore the 103 and wait for the subsequent response (which is hopefully a 200).”

The HTTP 103 Early Hints information response may be sent by a server while it is still preparing a response, with hints about the resources that the server is expecting the final response will link. This allows a browser to start preloading resources even before the server has prepared and sent that final response. The early hint response is primarily intended for use with the Link header, which indicates the resources to be loaded. It may also contain a Content-Security-Policy header that is enforced while processing the early hint. As explained here, this is an experimental feature.

Forum discussion at LinkedIn.