HTTP 103 Early Hints

In short: The server sends early hints about resources the browser can already load while the actual response is still being prepared.

In more detail: With Link headers using rel=preload or rel=preconnect the browser can prepare stylesheets, fonts or connections early. The final response (e.g. 200) follows on the same request.

In Depth

When it occurs

• The server needs a long time for the page (database) but already knows which files are needed.
• CDNs such as Cloudflare use 103 to shorten load time.

What you can do

1. As a visitor there is nothing to do.
2. Operators: only use it for resources that are really needed, otherwise bandwidth is wasted.

See also: HTTP Status Codes Overview, HTTP