files/en-us/web/http/reference/headers/sec-ch-prefers-reduced-motion/index.md
{{SeeCompatTable}}{{SecureContext_Header}}
The HTTP Sec-CH-Prefers-Reduced-Motion {{Glossary("request header")}} is a user agent client hint which indicates the user agent's preference for animations to be displayed with reduced motion.
If a server signals to a client via the {{httpheader("Accept-CH")}} header that it accepts Sec-CH-Prefers-Reduced-Motion, the client can then respond with this header to indicate the user's preference for reduced motion. The server can send the client appropriately adapted content, for example, JavaScript or CSS, to reduce the motion of any animations presented on subsequent rendered content. This could include reducing the speed or amplitude of movement to reduce discomfort for those with vestibular motion disorders.
This header is modeled on the {{cssxref("@media/prefers-reduced-motion", "prefers-reduced-motion")}} media query.
<table class="properties"> <tbody> <tr> <th scope="row">Header type</th> <td> {{Glossary("Request header")}}, <a href="/en-US/docs/Web/HTTP/Guides/Client_hints">Client hint</a> </td> </tr> <tr> <th scope="row">{{Glossary("Forbidden request header")}}</th> <td>Yes (<code>Sec-</code> prefix)</td> </tr> </tbody> </table>Sec-CH-Prefers-Reduced-Motion: <preference>
<preference>
no-preference or reduce.The client makes an initial request to the server:
GET / HTTP/1.1
Host: example.com
The server responds, telling the client via {{httpheader("Accept-CH")}} that it accepts Sec-CH-Prefers-Reduced-Motion. In this example {{httpheader("Critical-CH")}} is also used, indicating that Sec-CH-Prefers-Reduced-Motion is considered a critical client hint.
HTTP/1.1 200 OK
Content-Type: text/html
Accept-CH: Sec-CH-Prefers-Reduced-Motion
Vary: Sec-CH-Prefers-Reduced-Motion
Critical-CH: Sec-CH-Prefers-Reduced-Motion
[!NOTE] We've also specified
Sec-CH-Prefers-Reduced-Motionin the {{httpheader("Vary")}} header to indicate to the browser that the served content will differ based on this header value, even if the URL stays the same, so the browser shouldn't just use an existing cached response and instead should cache this response separately. Each header listed in theCritical-CHheader should also be present in theAccept-CHandVaryheaders.
The client automatically retries the request (due to Critical-CH being specified above), telling the server via Sec-CH-Prefers-Reduced-Motion that it has a user preference for reduced-motion animations:
GET / HTTP/1.1
Host: example.com
Sec-CH-Prefers-Reduced-Motion: "reduce"
The client will include the header in subsequent requests in the current session unless the Accept-CH changes in responses to indicate that it is no longer supported by the server.
{{Specifications}}
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