TLS

Name	URL	Comment
SSL/TLS Test	https://www.ssllabs.com/ssltest/
SSL/TLS Test	https://ssl-tools.net/

Browsers

HTTP headers Test	https://securityheaders.com/
IPLeak	https://ipleak.net/	Show what you are leaking
IPX	https://ipx.ac/run	Gives all the information about your browser
WebRTC	https://browserleaks.com/webrtc	WebRTC test

Subdomain finder	https://subdomainfinder.c99.nl/	Find hidden subdomains
DNS leak test	https://dnsleak.com
DNSSEC analyser	https://dnssec-analyzer.verisignlabs.com/	Visualisation of DNS Sec