To quickly perform HTTP compression test on
https://example.org execute command:
$ curl -s -I --compressed https://example.org | grep Content-Encoding
Empty result means that it doesn't support compression.
Alternatively, you can be more precise and define custom header.
$ curl -s -I -H 'Accept-Encoding: gzip,deflate' https://example.org | grep Content-Encoding >/dev/null && echo "It supports compression" || echo "It does not support compression"
It supports compression