What does HTTP 103 mean?
Lets the server send preliminary headers (such as Link preload) before the final response.
Common causes and when you see it
Used to speed up page loads by letting the browser start fetching CSS and JS early.
How to fix or handle it
Supported by modern browsers and CDNs. Safe to ignore in API clients.
Test it yourself
Send a request with the online API tester, inspect the response with the HTTP header checker, or host an endpoint that returns 103 with the mock API generator to see how your app reacts.
HTTP 103 questions
Lets the server send preliminary headers (such as Link preload) before the final response.
Used to speed up page loads by letting the browser start fetching CSS and JS early.
Supported by modern browsers and CDNs. Safe to ignore in API clients.