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http header

Sec-CH-Device-Memory header

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Secure contextLimited availability

The HTTP Sec-CH-Device-Memory request header is used in device client hints to indicate the approximate amount of available RAM on the client device, in gigabytes. The header is part of the Device Memory API.

Client hints are accessible only on secure origins. A server has to opt in to receive the Sec-CH-Device-Memory header from the client, by first sending the Accept-CH response header. Servers that opt in to the Sec-CH-Device-Memory client hint will typically also specify it in the Vary header to inform caches that the server may send different responses based on the header value in a request.

Header type [Request header](https://developer.mozilla.org/en-US/docs/Glossary/Request%20header), Client hint
[Forbidden request header](https://developer.mozilla.org/en-US/docs/Glossary/Forbidden%20request%20header) No

Syntax

Sec-CH-Device-Memory: <number>

Directives

  • <number>

    • : The approximate amount of device RAM.

      The amount of device RAM can be used as a fingerprinting variable, so values for the header are intentionally coarse to reduce the potential for its misuse. Values are only reported in powers of two, and are clamped to an implementation-defined minimum lower value and a maximum upper value. These bounds may change over time (see browser compatibility table).

      For example, if a browser does not report below 2 or above 32 then the value is one of: 2, 4, 8, 16, 32.

Examples

The server first needs to opt in to receive Sec-CH-Device-Memory header by sending the Accept-CH response header containing Sec-CH-Device-Memory:

Accept-CH: Sec-CH-Device-Memory

Then on subsequent requests the client might send Sec-CH-Device-Memory header back:

Sec-CH-Device-Memory: 1

Specifications

SpecificationsStandards references are available on the canonical MDN page.

Browser compatibility

Browser compatibilityCompatibility data is available on the canonical MDN page.

See also