IP test
ipinfo.io/92.222.68.44
Availability/reachability probing
https://atlas.ripe.net/
http://shotsherpa.com/
https://geopeeker.com/
https://www.geoscreenshot.com/
http://ipv6-test.com/validate.php
DNS
https://www.whatsmydns.net
https://dyn.com/free-dns-test/
https://www.dotcom-tools.com/DNS-lookup-tools.aspx
http://www.dnsstuff.com/tools
https://dnschecker.org/all-tools.php
Site perf test
https://developers.google.com/speed/pagespeed
https://tools.pingdom.com/
https://latency.apex.sh/
https://gtmetrix.com/
https://www.webpagetest.org/
TLS
https://wiki.mozilla.org/Security/Server_Side_TLS
https://mozilla.github.io/server-side-tls/ssl-config-generator/
https://www.ssllabs.com/ssltest/
https://tls.imirhil.fr/https
Client tests
https://www.ssllabs.com/ssltest/viewMyClient.html # browser tls
https://speedtest.net <a href="?addtag=speedtest" title="Hashtag speedtest">#speedtest</a>