ECT
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The ECT
Client hint request header field indicates the effective connection type: slow-2g
, 2g
, 3g
, 4g
.
Header type | Request header, Client hint |
---|---|
Forbidden header name | no |
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, while 4g
might be used to 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 in RTT
and Downlink
hints.
Syntax
http
ECT: <value>
Directives
- <value>
-
A value indicating effective connection type. This is one of:
slow-2g
,2g
,3g
, or4g
.
Examples
A server first needs to opt in to receive the ECT
header by sending the Accept-CH
response header containing ECT
.
http
Accept-CH: ECT
Then on subsequent requests the client might send an ECT
header back:
http
ECT: 2g
Specifications
Specification |
---|
Network Information API # ect-request-header-field |
Browser compatibility
BCD tables only load in the browser
See also
- Improving user privacy and developer experience with User-Agent Client Hints (web.dev)
- Network client hints
Accept-CH
- HTTP Caching > Vary and
Vary
NetworkInformation.effectiveType