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HTTP Status Code

103 Early Hints

Informational

The server is sending preliminary response headers before the final response is ready.

HTTP status code reference, response example, common causes, fixes, and related status codes.

What does HTTP 103 Early Hints mean?

HTTP 103 Early Hints is a status code sent by a server to indicate the result of an HTTP request.

Status codes help browsers, APIs, apps, and backend systems understand whether a request succeeded, failed, was redirected, or needs additional action.

In practice, HTTP 103 Early Hints usually appears when a server responds under specific request, validation, permission, or infrastructure conditions.

Response example

HTTP/1.1 103 Early Hints
Link: </styles.css>; rel=preload; as=style
Link: </app.js>; rel=preload; as=script

HTTP example

HTTP/1.1 103 Early Hints

Relevant headers

Link
Link: </styles.css>; rel=preload; as=style

Common causes

  • The server wants to help the browser preload critical resources early
  • Performance optimization for HTML pages
  • The server is sending preload hints before the final response

How to fix it

  • Verify that preload links are correct and actually needed
  • Only send Early Hints for resources that will be used by the final response
  • Test browser, proxy, and CDN support before relying on it in production

Common mistakes

  • Assuming the status code alone explains the full backend issue
  • Ignoring related response headers that add important context
  • Treating temporary errors as permanent failures
  • Retrying too aggressively without checking the cause
  • Debugging the frontend only when the problem is server-side

How browsers and APIs use it

Browsers, APIs, and backend services use HTTP status codes to understand the outcome of a request. Depending on the status code, an application may render content, retry a request, redirect the user, show an error, or trigger a different flow in the client or server.

Practical developer insight

103 Early Hints is mainly used as a performance optimization. It lets browsers start loading CSS, JavaScript, fonts, or other critical resources before the final response arrives. It is also considered a modern alternative to the deprecated HTTP/2 Server Push mechanism.

Client-side example

if (response.status === 103) {
  console.log("Server sent early preload hints.");
}

Related status codes

HTTP 102HTTP 200HTTP 304