Folders is a non-textual esoteric programming language created in 2015, updated 2026, by the creator of Rivulet and Velato. It ranks as one of forty-four esolangs, where code is expressed through containment and order alone. Folder names are ignored except for alphabetical ordering, making programs pure ordered trees. Inspired by the Whitespace language, Folders explores dematerialized code, beginning with the question: what is more empty than a file with no visible text? The empty folder is seen as clutter with no purpose, ignored entirely in git. Folders began as a Windows language, where folders take up no disk space at all. Creating 352,449 folders and checking properties demonstrates this, offering infinite storage capacity. All data can be encoded in folder names, bypassing the material realm of files entirely. For non-Windows users, an emulator provides some experience of how Folders manages data and code. The original implementation is available on GitHub.
Each command folder has at least one child folder. The number of subfolders in the first folder (alphabetically) indicates the command type; arguments appear in a second folder; some commands require a third. Expressions work similarly: the number of folders in the first sub-folder determines the expression type. Temporary data is stored as folders, where the name holds the data itself.
The Folders interpreter avoids temp files, storing anything not immediately in memory as temp folders. Preferred I/O uses another set of folders, encoding all data in folders for infinite disk space (attempt at your own risk).
A Folders program is a nil-terminated nested list, visualized as pure containment and order. Examples include a Fibonacci program saved as JSON arrays and a Truth Machine as a contour map. Other visualizations include family trees, botanical structures, or maze paths.
Source: Hacker News · Summarized by HeadlinesBriefing