103 Early Hints
Allows the server to send preliminary response headers while it prepares the full response.
Used to return some response headers before final HTTP message.
What HTTP 103 Early Hints Means
Used to return some response headers before final HTTP message.
Allows the server to send preliminary response headers while it prepares the full response.
Common Causes
- Server sending Link headers for preloading resources
- Performance optimization
What Visitors Should Do
- This is not an error - performance optimization in progress
Notes for Developers
- Use to preload critical resources
- Send Link headers for CSS, JS, fonts
How 103 Early Hints Works
A server can send one or more 103 interim responses before the final response. They usually carry Link headers so the browser can start preloading critical resources while the server is still building the page:
HTTP/1.1 103 Early Hints
Link: </css/main.css>; rel=preload; as=style
Link: <https://fonts.example.com>; rel=preconnect
HTTP/1.1 200 OK
Content-Type: text/html
...Browsers treat Early Hints as a performance hint only: if a client does not understand 103, it simply waits for the final response. Chromium-based browsers act on Early Hints only over HTTP/2 or HTTP/3, and CDNs such as Cloudflare can generate them from the Link headers of earlier responses.
Frequently Asked Questions
What does HTTP 103 Early Hints mean?
Allows the server to send preliminary response headers while it prepares the full response. In short: Used to return some response headers before final HTTP message.
How should I handle an HTTP 103 Early Hints response?
Use to preload critical resources. Send Link headers for CSS, JS, fonts.
Official Specification
The 103 Early Hints status code is defined in RFC 8297.