HTTP 103 Early Hints

HTTP 103 Early Hints — An interim response carrying Link headers so the browser can preload resources while the server prepares the real response.

Class

1xx Informational

Defined in

RFC 8297

Official

Yes (IANA registry)

What does HTTP 103 mean?

Lets a server (or CDN) send Link: </style.css>; rel=preload; as=style immediately, before the final 200 is ready, so the browser starts fetching critical CSS, fonts or preconnecting to origins. Chrome, Edge, Firefox and Safari support it for preload/preconnect; Cloudflare and Fastly can generate it from cached Link headers.

Handling 103

1. Visitors: You'll never see this in a browser — it's an interim response handled automatically before the final status.
2. Developers: Your HTTP client handles 1xx responses internally; fetch() never exposes them. Inspect them with curl -v or a packet capture.

Example 103 response

HTTP/1.1 103 Early Hints
Link: </styles/main.css>; rel=preload; as=style
Link: <https://fonts.gstatic.com>; rel=preconnect

1xx Informational: Interim responses: the request was received and processing continues. See the full list of HTTP status codes.

Related status codes

• 200 OKThe request succeeded and the response contains the result.
• 100 ContinueThe server received the request headers and the client should go ahead and send the body.

Related tools

• HTTP status codes — full list
• HTTP headers reference
• cURL converter
• Mock API — fake REST endpoints with custom status codes