> experimental feature with no standardization
Web Packaging was originally proposed in 2015 as a W3C draft (https://www.w3.org/TR/2015/WD-web-packaging-20150115/) and the Signed Exchanges spec as an IETF specification (https://wicg.github.io/webpackage/draft-yasskin-http-origin-...)
There is also an open source project implementing it that anyone can use (https://github.com/ampproject/amppackager).