UA-(CPU, Disp, OS, Color, Pixels)

UA-(CPU, Disp, OS, Color, Pixels)

 

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These User-Agent headers are nonstandard and no longer common. They provide information about the client machine that could allow for better content selection by a server. For instance, if a server knew that a user's machine had only an 8-bit color display, the server could select images that were optimized for that type of display.

With any header that gives information about the client that otherwise would be unavailable, there are some security concerns (see Chapter 14 for more information).

Type

Extension request headers

Notes

These headers are not defined in RFC 2616, and their use is frowned upon.

Basic Syntax

"UA" "-" ("CPU" | "Disp" | "OS" | "Color" | "Pixels") ":" machine-value

machine-value = (cpu | screensize | os-name |display-color-depth)

Examples

UA-CPU: x86	CPU of client's machine
UA-Disp: 640, 480, 8	Size and color depth of client's display
UA-OS: Windows 95	Operating system of client machine
UA-Color: color8	Color depth of client's display
UA-Pixels: 640x480	Size of client's display