Internet

"People probably don't realise that I don't actually like the internet much at all. Though I pioneer its woods, I consider them cruel and unforgiving, and advise others to steer clear altogether. Probably like real explorers used to do."

- Homestuck Book 2 commentary

The internet is one of Sburb's requirements of a regular session, and as a consequence it exists in all Homestuck universes. While it can fail to work in HS 2190 ("real life"), players in the incipisphere have stable and unlimited acess to it along with electricity for their homes.

The denizen of each Homestuck player matches their internet browser of choice, and the browser icons are simplified representations of the denizens' appearances.

Alternia has its own internet, but the trolls can acess human websites on the incipisphere after getting their urls. Fedorafreak can communicate with the kid's universe from his session too, so all universes' web are interchangable between the incipisphere, with the exception of alternate timelines (and consequently, scratched universes). Data can also be hosted into servers in the Furthest Ring, where it can be acessed by anyone and is safer to be preserved.

It's safe to assume that all real life websites have existed inside Homestuck until the date of the kids' entry.

Notable programs that use internet connection

 * Sburb and related apps like GristTorrent;
 * Web browsers;
 * Many chat clients are connected to eachother and are used during the sessions for communication. Trollian specially allows to see users in different points of their timelines and message with them;
 * Serious Business and Delirious Biznasty work in a similar way to Twitter;
 * Rebelgram in Hiveswap, who works similar to Instagram;
 * Snapchat (or a similar program).

While not part of the internet, simplier devices like walkie-talkies have been used and some robots could be remotely controlled by their owners. The many Sburb apparel can also interact with players and their planets from different points of the timeline.

MS Paint Adventures
MSPA's own website existed inside Homestuck and the kids were their readers. Confirmed adventures to exist are Homestuck, Midnight Crew, Problem Sleuth and Problem Sleuth 2 in post-scratch 2011. The Midnight Crew's url is visible on HS 2012 (this page) and in real life directs to the image of a spade caked in blood.

The MSPA Reader acessed it too, much to his dismay.

Plush Rump
Dave's Bro owned a website of erotic puppet videos, some apparently involving humans, raking by a PayPall account. A chat existed on the site's bottom.

Zillyloot
A self-declared Kickstarter parodyHS 8839, probabily owned by Caliborn where he funded his masterpiece with his own currency, which resemble BitCoins. All backers were his minions, mostly because he lived in a post-apocalypitc wasteland.

Scythian
One of the few alternian websites mentioned, Scythian is a parody of Amazon with "certain things off limits or too expensive for trolls lower in the blood-caste system." Xefros has ordered Flarp manuals through this service.

Social Media
Dave used to run a number of ironically humorous blogs, websites and social networking profiles not shown onscreen, except for one that also exists on real life. He was the creator of Sweet Bro and Hella Jeff and owned its website as well.

Since Delirious Biznasty and Serious Business work like Twitter, it's possible they have a website and the programs are just a quick way to acess them.

Jade was seen browsing FurAffinityHS 2734, though it's unclear if she used to have an account.

After Caliborn took over the narrative, he created a real life DeviantArt account where he hosted some of his drawings and a not-so-real Vine account to show his masterpiece.

Vriska Serket either had a Vriskagram account or owned the website. There, many pictures of the post-scratch meteor journey were posted. A real life account exists on Instagram: TheVriskaSerket.

Prongle is an Alternian network that works like Twitter, but with the opition to hate posts.

Other
Some websites are found on Dave and Bro's content aggregator, mostly for puppets, blogs and news. It is seen that Skaianet had a website and CNN (a real news website) had breaking news about a meteor crash. plushrump.com (one of the site's titles) redirects to HS 2360 (this page).

Tinyurl is the external website most seen in Homestuck. Characters use this url shortener to send pictures (hosted on real life at MSPA) and YouTube videos to others.

Rose hosted her walkthrough of Sburb in GameFAQs, and a copy of it was uploaded in the Furthest Ring and repassed to other universes by the Horrorterrors. Some players from other sessions did walkthroughs too but, according to Homestuck's book commentary, they ended dead before completing it.

In Problem Sleuth
Even the recession era has internet inside MSPA. When PS got fed of boring/hard puzzle shit, he checked GameFAQs to see the intended solution to the plight of the four kingdoms (that is cheating with the Code Machine). Some of the usernames seen are also present when Rose checked GameFAQs in Homestuck.