HTTP 103 Early Hints and performance
103 Early Hints is an informational status that lets a server send hints — typically Link headers for preloading or preconnecting — before the final response is ready. Browsers can start fetching critical assets earlier, improving load time. It is a performance optimisation that sits ahead of the eventual 200 a crawler processes.
What 103 means
103 Early Hints is an informational (1xx) status used to send the client some response headers — most usefully Link headers indicating resources to preload or origins to preconnect — before the server has finished preparing the final response.
It is interim by design: the client should expect a final response (such as 200) to follow. Early Hints lets the browser begin fetching critical CSS, fonts, or scripts during the time the server is still assembling the page.
103 and performance
If a server takes time to generate a page (think server-side rendering or a slow data fetch), the browser would normally sit idle until the full response arrives. 103 Early Hints fills that gap: the browser receives preload hints early and starts retrieving critical assets in parallel, so they are ready when the final HTML lands.
For crawlers, the important point is that 103 does not change what gets indexed — the final response and its body are still what the crawler evaluates. Early Hints is a speed optimisation that benefits real users and, indirectly, page-experience signals tied to load performance.
- 103 carries preload/preconnect hints before the final response
- A final status (e.g. 200) still follows and is what gets indexed
- Improves perceived load time by fetching assets earlier
Operator checklist
Use 103 Early Hints to preload genuinely critical assets when server response generation is slow. Confirm the final response still returns the correct status and full body. Verify your CDN or edge supports forwarding 1xx responses, since not all infrastructure does.
How it appears in analytics and logs
A 103 is an interim informational response carrying preload/preconnect hints before the final status. It does not replace the final response; the crawler still receives and processes the eventual 200 (or other final status) and its body.
Diagnostic use case
Speed up page rendering by sending preload hints early, and understand that 103 precedes, rather than replaces, the final response crawlers index.
What WebmasterID can help detect
WebmasterID focuses on the final responses crawlers receive; 103 is an interim hint that precedes them. It can still help you observe whether pages ultimately return healthy final statuses.
Common mistakes
- Expecting 103 to replace the final response — a final status still follows.
- Sending Early Hints through infrastructure that drops 1xx responses.
- Preloading non-critical assets, adding contention rather than speed.
Privacy and accuracy notes
Status codes carry no personal data. WebmasterID reports response patterns for crawler traffic without exposing individual visitors.
Related pages
- HTTP 200 OK: what it means for crawlers
200 OK means the request succeeded and the server returned the resource. For crawlers it is the green light to process and potentially index a page. The subtle trap is the soft 404 — an error or empty page served with a 200 status, which wastes crawl budget and pollutes the index.
- JavaScript rendering and crawling
Content injected by JavaScript is not in the initial HTML, so a crawler must render the page to see it. Rendering is more expensive than fetching HTML, and not all crawlers render. Server-side rendering (SSR) or prerendering puts content in the HTML directly, reducing dependence on the crawler's render step.
- Website observability
See the final status codes your pages return to crawlers.
Sources and verification notes
Last reviewed 2026-06-24. Facts are checked against primary/official sources where available; uncertain specifics are marked “Data not yet verified” rather than guessed.