There are many good command line tools to measure websites' performance. We have compiled a list of particularly useful online tools here, so that our customers could run different tests and checks for their Drupal, Backdrop and WordPress projects on AltaGrade servers.
Performance, Traffic, SEO
https://gtmetrix.com
http://www.webpagetest.org
https://developers.google.com/speed/pagespeed/insight
https://tools.pingdom.com
https://isvarnishworking.uk
https://ahrefs.com
https://majestic.com
https://moz.com
https://pagespeed.web.dev
https://validator.w3.org
https://web.dev
https://tools.bunny.net
DNS
http://www.intodns.com
http://www.dnsstuff.com
http://www.dnsqueries.com
https://www.whatsmydns.net
https://toolbox.googleapps.com
https://xnnd.com
https://tools.wordtothewise.com/
Geo-tools, pingers, trackers
http://host-tracker.com
http://www.infobyip.com
http://www.ip2location.com
http://www.mxtoolbox.com
http://www.senderbase.org
http://multirbl.valli.org/lookup
https://dmarcian.com/spf-survey
https://toolbox.googleapps.com/apps/checkmx
https://www.port25.com/authentication-checker
https://dkimvalidator.com
https://dkimcore.org/tools/keycheck.html
https://www.mail-tester.com
http://www.isnotspam.com
https://toolbox.googleapps.com
https://tools.wordtothewise.com/authentication
https://www.checktls.com
https://www.caniemail.com
https://temp-mail.org/en
https://tools.appriver.com/OpenRelay.aspx
Drupal
http://isthissitebuiltwithdrupal.com
https://isvarnishworking.uk
SSL
https://www.ssllabs.com/ssltest
https://whatsmychaincert.com
https://decoder.link/sslchecker
https://hackertarget.com/ssl-check/
Online scanners
https://www.virustotal.com
https://metadefender.opswat.com
https://www.hybrid-analysis.com
https://urlscan.io
https://observatory.mozilla.org
https://pentest-tools.com
https://www.upguard.com
https://www.immuniweb.com/websec
https://snyk.io/website-scanner
Miscellaneous
https://www.explainshell.com
https://websemantics.uk/tools/image-to-data-uri-converter
https://www.ssh.com/iam/password/generator
https://passwordsgenerator.net
https://onetimesecret.com
https://www.mailinator.com
https://toolbox.googleapps.com
http://jigsaw.w3.org/css-validator
https://www.dotomator.com
https://caniuse.com
https://www.pexels.com
https://quillbot.com
https://www.loom.com
https://tinywow.com
https://www.poptox.com
https://www.pdfdrive.com
https://12ft.io
https://hemingwayapp.com