An instant messenger client, and the troll version of Pesterchum. It features a chumpRoll, a sort of reverse version of the trollSlum. According to Karkat's interface, all the other trolls as well as himself are listed on the Chumproll. Whether this is a part of Trollian or Karkat's personal preference is unknown. The trolls use the program when trolling the kids, allowing the user to communicate with each kid listed on the chumpRoll, as well as access a visual feed using the view port, at any point in that person's time line. The interface includes grey bars that indicate when each person on the timeline entered the Medium.

Each troll has a Trollian pseudonym, made up of two words, generally related to their associated zodiac sign and/or characteristics. The abbreviations for these pseudonyms are composed of DNA bases A, C, G, and T, and together with the Kid's handles, comprise all sixteen possible combinations of these letters.

The name is based on the Trillian instant messenger client.

Trollian has a bulletin board function that allows users to post notes that are visible to other users in both the past and the future. Naturally Karkat abuses this function in a hilariously self-defeating way, to the point where he bans himself from different points in the timeline three different times. The length of these bulletin board bans is unknown, since Karkat repeatedly gets banned by Terezi and begins responding again without being unbanned in this chat, each ban spanning only about 1-3 minutes. The boards also allow for conversations with more than two people at once.

In Hivebent, Karkat tries out the beta version of Trollian to talk to the other trolls, all of whom seem to already have it.

When Kanaya scrolls up into the future of the trolls' timelines, she only sees bright lights and swirling black and white lines.

Doc Scratch is able to communicate with Trollian users, despite using a typewriter.

Speculation

It seems that the trolls cannot be blocked. Whether this is an inherent feature of Trollian or the work of a certain hacker has yet to be seen. Later, Terezi is blocked by Karkat due to Gamzee using her glasses, and receives the error "did not receive message" when she attempts to contact him. Eridan also seems to have been blocked by Vriska at some point in time.

It has been speculated that Davesprite has access to Trollian when using his iShades, as his conversation with Terzi begins with "turntechGodhead [TG] began trolling gallowsCalibrator [GC]'. However, this is very unlikely since he lost all contact with the trolls after the timeline split; In his conversation with Alternate Future Rose, Alternate Future Dave (later Davesprite) mentioned that neither of them heard from the trolls again, because Trollian is limited to the one, non-doomed, timeline.

Although the trolls claim to be able to chat with the kids at any point in their timeline, they later admit they cannot see or talk to the kids after The Scratch, most likely because the Scratch will have reset their entire universe.