[4] User-generated content can be uploaded and categorized into either one of the site's four web portals: Games, Movies, Audio, and Art.

[5][6] Since Adobe Flash Player was shut down on most browsers by late 2020, Newgrounds uses the Ruffle emulator, an Adobe Flash emulator written in Rust and sponsored by Newgrounds along with other popular sites like Cool Math Games and Armor Games.

Art and Audio are processed using a different method called "scouting", which the site describes as "a way to vet users and weed out spam, stolen works, low quality submissions, etc."

Like the judgment system, it stops stolen content, spam, or prohibited material reaching the public area, relying on users and site moderators.

[9] Content and context are liable to be reported for review to the moderators and staff members by flagging it for violations to the site's guidelines.

[18][19] In 1991, at the age of 13, Tom Fulp launched a Neo Geo fanzine called New Ground and sent issues to approximately 100 members of a club originating on the online service Prodigy.

[20] Using a hosting service, he launched a website called New Ground Remix in 1995, which increased in popularity during the summer of 1996 after Fulp created the BBS games Club a Seal and Assassin while a student at Drexel University.

[19] It subsequently became one of the most "active Flash creator communities in the English-speaking Internet" and served as a place that video game developers could begin their careers.

[39] In September 2023, an update to the site's Art Portal was rolled out, implementing it in the existing Project system for animation, games and audio, as well as adding the ability to use multi-author credits on Art submissions and adding multi-art support in either Inline, Strip or Gallery formats.