103 Early Hints

Interim response carrying Link headers so the browser can preload or preconnect before the final response is ready.

103 at a glance

Code: 103
Name: Early Hints
Class: 1xx Informational
Status: IANA-registered standard code
Defined in: RFC 8297, Section 2
Cacheable by default: No. Interim (1xx) responses are never stored by caches.

What 103 means

103 Early Hints (RFC 8297) lets a server, or a CDN in front of it, send Link: rel=preload and rel=preconnect headers while the application is still building the page. The browser starts fetching CSS, fonts or connecting to third-party origins during "server think time", which improves Largest Contentful Paint. The final 200 follows on the same request.

What typically causes a 103

Cloudflare Early Hints, which caches Link headers from earlier 200 responses and replays them as a 103.
Frameworks and servers that support it natively (nginx 1.29+ with early_hints, H2O, Node.js response.writeEarlyHints(), Rails).

Fix it on the server

Only hint resources the page really needs; unused preloads waste bandwidth.
Chrome acts on 103 for top-level navigations over HTTP/2 and HTTP/3, and only for preconnect and preload hints.
Some older HTTP/1.1 clients mis-handle interim responses, so many servers send 103 only over HTTP/2+.

Fix it as a client or visitor

Nothing to fix: clients that do not understand 103 must ignore it. In DevTools the hinted requests show "Early Hints" as initiator.

Headers that go with 103

Header	Role
`Link`	Resources to preload or origins to preconnect, e.g. `</style.css>; rel=preload; as=style`.

Example response

HTTP/1.1 103 Early Hints
Link: </style.css>; rel=preload; as=style
Link: <https://cdn.example.com>; rel=preconnect

HTTP/1.1 200 OK
Content-Type: text/html