[Santosh83]

> Cloudflare and Firefox devs cooperate to implement drafts of eSNI, so if you have a recent Firefox and a site which has opted into Cloudflare's trial of this feature, then it works for you, ...

Well, at least not yet with the latest release version of Firefox (v69). Tested with Cloudflare's own page for testing eSNI browser support (and TLS 1.3, DNSSEC & DoH). Firefox supports the other three but not eSNI, according to that page. Even the Dev channel (v71) has no support.

https://www.cloudflare.com/ssl/encrypted-sni/

[pritambaral]

It's not enabled by default, and not exposed under browser preferences. It's available in about:config under network.security.esni.enabled.