its like gzip only quicker and smaller compressions.

Smaller yes (mainly on english), but quicker not,

On decompression it is a little slower than gzip, so it is fine,
but it is multiple times slower when compressing,
-- in fact from what i have read it is silly slow e.g. 25x slower than gzip, ??
and thus not suitable for dynamic pages

Enabling it on web-sites that only have a few pages and combine it with Joomla page caching, then maybe
-- but on sites with filter forms and a lot of content, it will eat your CPU resources fast

If this is added it should be configurable to use it only on specific pages for which page caching is enabled too

see: https://quixdb.github.io/squash-benchmark/

its slower yes, but not 25x

its slower yes, but not 25x

Right,
my comment was partly incorrect, it is 10x-25x slower only at its maximum compression ratio, comparing to level 5 or 6 of gzip (more than this gives little no benefits),

-- when targeting a double compretion ratio than gzip it is only 15%-30% slower than gzip

so yes, it is worthwhile using it instead of gzip

yes, it seems brotli is going to get wide use but not yet supported by every vendors, for instance, nginx does not support it yet in the core, edge still does not support it, neither safari (http://caniuse.com/#feat=brotli).

But IETF published an information RFC (https://tools.ietf.org/html/rfc7932) and many vendors are moving in to support it. So it's problable that it will be a gzip/deflate alternative soon.

I think it's responsibility of server (apache/ ngix/ iis), not an application.

Although at this moment we have an option in global configuration to enable gzip compression for html output, I prefer to set it in the .htaccess file because I can configure there compression of other resources too.

Compression of html output makes relatively small impact compared to other resources (js/ css/ images) which must be configured outside application anyway.

I think it's responsibility of server (apache/ ngix/ iis), not an application.

Agree, but ... the same is valid for gzip ... which joomla supports ...

Closing this here because there is a RFC for 4.0 #15804 and we don't need two open issues.