Screaming Frog SEO Spider - The Screaming Frog SEO Spider is a small desktop program (PC or Mac) which crawls websites’ links...
OpenSSL - OpenSSL is a free and open source software cryptography library that implements both the Secure Sockets Layer (SSL) and the Transport Layer Security (TLS) protocols, which are primarily used to provide secure communications between web browsers and …
Xenu's Link Sleuth - Xenus Link Sleuth checks Web sites for broken links.
Ensighten - Ensighten provides enterprise tag management solutions that enable businesses manage their websites more effectively.
Integrity - Feature comparison of link checkers for Mac: Integrity, Integrity Plus and Scrutiny
Let's Encrypt - Let’s Encrypt is a free, automated, and open certificate authority brought to you by the Internet Security Research Group (ISRG).