In the Silver Age, Superman’s hair and fingernails didn’t grow. (I’m not sure whether it was addressed in the Golden Age.) This implies that Superman has the exact same haircut that Jor-El and Lara gave him as a baby, which was also never addressed, as far as I know.
In Action Comics #300 from 1963, Superman ends up in the far future, when the sun has turned red, so he loses his powers. Losing his powers makes his hair and fingernails grow. As he figures out how to get back to his own time, he makes a point to cut his hair and fingernails before his powers come back, since otherwise, there would be no way to cut them afterward.
Later renditions are a completely different story, of course. Mostly, I’ve seen him use heat vision to cut his hair, with an occasional kryptonite-laced razor or scissors. I don’t remember any version showing him cut his nails, other than Action #300.
Those covers are great.
In the Silver Age, Superman’s hair and fingernails didn’t grow. (I’m not sure whether it was addressed in the Golden Age.) This implies that Superman has the exact same haircut that Jor-El and Lara gave him as a baby, which was also never addressed, as far as I know.
In Action Comics #300 from 1963, Superman ends up in the far future, when the sun has turned red, so he loses his powers. Losing his powers makes his hair and fingernails grow. As he figures out how to get back to his own time, he makes a point to cut his hair and fingernails before his powers come back, since otherwise, there would be no way to cut them afterward.
Later renditions are a completely different story, of course. Mostly, I’ve seen him use heat vision to cut his hair, with an occasional kryptonite-laced razor or scissors. I don’t remember any version showing him cut his nails, other than Action #300.