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Client Hints are a set of HTTP headers and a JavaScript API that allow web browsers to send detailed information about the client device and browser to web servers.

User-Agent String
user-Agent
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User-Agent Client Hints (JavaScript API)
API Support
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Architecture
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bitness
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Brands (Browser brands)
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Full Version List
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mobile
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model
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platform
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Platform Version
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User Agent Full Version
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WOW64 (32-bit on 64-bit Windows)
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Request Headers (User-Agent Client Hints)
sec-ch-ua
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sec-ch-ua-platform
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sec-ch-ua-mobile
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sec-ch-ua-full-version
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sec-ch-ua-platform-version
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sec-ch-ua-full-version-list
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sec-ch-ua-arch
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sec-ch-ua-bitness
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sec-ch-ua-wow64
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sec-ch-ua-model
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sec-ch-save-data
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sec-ch-width
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sec-ch-viewport-width
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viewport-width
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sec-ch-viewport-height
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sec-ch-dpr
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dpr
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sec-ch-device-memory
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device-memory
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sec-ch-rtt
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sdownlink
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sec-ch-ect
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ect
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sec-ch-prefers-color-scheme
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sec-ch-prefers-reduced-motion
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sec-ch-prefers-reduced-transparency
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sec-ch-prefers-contrast
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sec-ch-forced-colors
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sec-ch-ua-form-factors
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Known Client Hints Headers (Reference)
  • Sec-CH-UA
    Represents the browser brand(s) and major version.
  • Sec-CH-UA-Full-Version
    Indicates the full browser version string. (Deprecated, replaced by Sec-CH-UA-Full-Version-List)
  • Sec-CH-UA-Full-Version-List
    Indicates the full browser version string.
  • Sec-CH-UA-Platform
    Represents the platform for a given user agent.
  • Sec-CH-UA-Platform-Version
    Represents the platform version for a given user agent.
  • Sec-CH-UA-Arch
    Represents the architecture of the platform for a given user agent.
  • Sec-CH-UA-Bitness
    Indicates the bitness of the platform architecture on which the given user agent is executing
  • Sec-CH-UA-WoW64
    Indicates whether the browser is running in 32-bit mode on 64-bit Windows.
  • Sec-CH-UA-Model
    Represents the device executing the given user agent.
  • Sec-CH-UA-Mobile
    Indicates whether the user agent prefers a mobile experience.
  • Sec-CH-UA-Form-Factors
    Indicates the device form factor, historically represented by the deviceCompat token in User-Agent strings.
  • Sec-CH-Lang
    (or Lang) Represents the user's language preference.
  • Sec-CH-Save-Data
    (or Save-Data) Indicates the user agent's preference for reduced data usage.
  • Sec-CH-Width
    Provides the layout width of the image resource request in CSS pixels.
  • Sec-CH-Viewport-Width
    (or Viewport-Width) The width of the user's viewport in CSS pixels.
  • Sec-CH-Viewport-Height
    Represents the current viewport height of the user agent.
  • Sec-CH-DPR
    (or DPR) Reports the ratio of physical pixels to CSS pixels on the user's screen.
  • Sec-CH-Device-Memory
    (or Device-Memory) Indicates the approximate amount of device memory in GiB. Because this information could be used to identify users, Device-Memory values are deliberately coarse. Valid values are 0.25, 0.5, 1, 2, 4, and 8.
  • Sec-CH-RTT
    (or RTT) Provides the approximate round-trip time at the application layer, in milliseconds. This RTT includes server processing time and differs from transport-layer RTT. Values are rounded to the nearest 25ms to prevent fingerprinting.
  • Sec-CH-Downlink
    (or Downlink) Represents the approximate downlink speed of the user's connection in megabits per second (Mbps). Values are rounded to the nearest multiple of 25 kilobits per second (kbps) to prevent fingerprinting.
  • Sec-CH-ECT
    (or ECT) Stands for Effective Connection Type, as estimated by the browser. Its value is one of an enumerated list of connection types, each describing a connection within a specified range of RTT and downlink values. Valid ECT values are '4g', '3g', '2g', and 'slow-2g'.
  • Sec-CH-Prefers-Color-Scheme
    Indicates the user's preferred color scheme.
  • Sec-CH-Prefers-Reduced-Motion
    Indicates whether the user has requested the system to minimize the amount of animation or motion it uses.
  • Sec-CH-Prefers-Reduced-Transparency
    Indicates whether the user has requested the system to minimize the number of transparent or semi-transparent layer effects it uses.
  • Sec-CH-Prefers-Contrast
    Indicates whether the user has requested web content to be presented with higher (or lower) contrast.
  • Sec-CH-Forced-Colors
    Indicates whether the user agent has enabled forced colors mode, where it enforces a user-chosen limited color palette on the page.
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