The HTTP Upgrade-Insecure-Requests request header sends a signal to the server expressing the client’s preference for an encrypted and authenticated response, and that it can successfully handle the upgrade-insecure-requestsCSP directive.
A client requests signals to the server that it supports the upgrade mechanisms of upgrade-insecure-requests:
GET / HTTP/1.1
Host: example.com
Upgrade-Insecure-Requests: 1
The server can now redirect to a secure version of the site. A Vary header can be used so that the site isn't served by caches to clients that don’t support the upgrade mechanism.
The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.
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