There is one very brief scene of nudity in Homestuck, though there are a few sexual innuendos throughout the webcomic.

A line from the homestuck webcomic that a troll says : "GA: Um Is This. GA: A Common Sort Of Practice In Human Courtship. GA: Watching Oblong Meat Products Tumble Into Places They Dont Belong". A young child wouldn't be able to catch what it means.

Depictions of sexuality. Could be taken sexually.

There are some pretty gruesome scenes, which may disturb younger viewers, though the simplistic art style of the webcomic makes it more mild.

There are some violent moments where the art style changes itself up to emphasize the carnage and gore.

Homestuck often includes profanity. "F-bombs" are often dropped.

Homestuck is well-known for it's frequent profanity, webcomic and show.

In the webcomic, on John's desktop, there is a file titled "FUCK FUCK FUCK. ^CAKE" it is a file of John's carrot cake for his birthday.

As far as I remember of the series, there is very little drug use in Homestuck. One of the only things drug related in the series is a drug used by the alien species, trolls, which is very obviously similar to marijuana. In the webcomic, there is also a good amount of alcohol use by certain characters.