catbox.moe works with SSL to old Apple Safari, but that link of yours fails to be a supported https conneciton to old safari. I tested it now. pic8 should switch to "Let's Encrypt R3", since its more compatible with more browsers, for now. EDIT : Apple Safari on IPhone 6 Plus running iOS 8.4 FAILS to connect using HTTPS SSL to pic8.co but WORKS with catbox.moe. pic8.co also fails on other Apple machines. Its use of X25519 might be the problem with pic8.co on older browsers. Apple does not like servers FORCED in web server code to only serve X25519 on port 443, and older Apple browsers prefer using TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA384 (BOTH secp521r1:secp384r1 should be allowed) suite B : https://tools.ietf.org/html/rfc6460 Apple is being pedantic and strict and is trying to comply with Suite B. Suite B restricts the curves to P-256 and P-384 TL/DR : pic8.co is broken for widespread HTTPS, and catbox.moe web server is not broken, even though they both have the same exact identical types of SSL certs. Its a web server fuckup at pic8.co, and can be fixed with one line of change on pic8 server to set "ssl_ecdh_curve' to secp521r1:secp384r1.