64 characters picked at random in [a-zA-Z0-9_] is perfectly fine if password is your only option. Special character do not increase significantly the difficulty of bruteforcing it, but introduce the risk of having to manually type "}à.å÷Â!!ç-×ô@¸Á¢±ãÕß>>úÓ}¼º¤«<_`àÅû§Æ]*ÂñçÌÿ§à®&ܱ=Ú-´ð¹é$.>=;Ö if something goes catastrophically wrong.
64 characters picked at random in
[a-zA-Z0-9_]
is perfectly fine if password is your only option. Special character do not increase significantly the difficulty of bruteforcing it, but introduce the risk of having to manually type"}à.å÷Â!!ç-×ô@¸Á¢±ãÕß>>úÓ}¼º¤«<_`àÅû§Æ]*ÂñçÌÿ§à®&ܱ=Ú-´ð¹é$.>=;Ö
if something goes catastrophically wrong.Not being allowed to use special characters can be a sign of the website saving your password in plain text.