ECT header

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

Experimental:This is anexperimental technology
Check theBrowser compatibility table carefully before using this in production.

The HTTPECTrequest header is used inClient Hints to indicate theeffective connection type:slow-2g,2g,3g, or4g.

The value represents the "network profile" that best matches the connection's latency and bandwidth, rather than the actual mechanisms used for transferring the data.For example,2g might be used to represent a slow Wi-Fi connection with high latency and low bandwidth, while4g might represent a fast fibre-based broadband network.

The hint allows a server to choose what information is sent based on the broad characteristics of the network. For example, a server might choose to send smaller versions of images and other resources on less capable connections. The value might also be used as a starting point for determining what information is sent, which is further refined using information inRTT andDownlink hints.

Note:A server that specifiesECT inAccept-CH may also specify it inVary to indicate that responses should be cached for different ECT values.