An outliner (or outline processor) is a specialized type of text editor (word processor) used to create and edit outlines, which are text files which have a tree structure, for organization. Textual information is contained in discrete sections called "nodes", which are arranged according to their topic–subtopic (parent–child) relationships, like the members of a family tree. When loaded into an outliner, an outline may be collapsed or expanded to display as few or as many levels as desired.

— From Wikipedia, the free encyclopedia

Outliners overlap with note-taking apps, often by a lot. Also many of them support time tracking, task lists and so on.

This document provides a brief look at well-known, popular or otherwise relevant software in these categories, along with lesser known and adjacent apps.

License

• The 800-pound gorilla of outliners is Org Mode.

Some are only kept around by nostalgia:

• hnb a curses program to structure many kinds of data in one place ancient, abandoned and awkward

Unusual

• TreeSheets Free Form Data Organizer (Hierarchical Spreadsheet) a pretty cool concept it turns out, in active development as of late 2023
• TreeLine is arguably more of a personal database (see review in other file) with nested records; still developed as of late 2020

Mobile

• Orgzly: Outliner using org files (see below) to import/export data. It helps to know a few things about this file format, for example how to set a notebook title and what drawers are. Orgzly focused on agenda features, but is equally good for notes or planning.

File formats

• Org files are the underlying format of Org Mode. While complex, a decent subset can be parsed easily enough. Compatible apps include Orgzly (and others not mentioned here).
• OPML is an old and much maligned format, nowadays mostly used by RSS readers to exchange lists of feeds; hnb can use it.

Links

• OutlinerSoftware.com, an active forum (as of mid-2022)
• The OrgDown initiative lists many apps with support for org files.

Note-taking (sometimes written as notetaking or note taking) is the practice of recording information from different sources and platforms. By taking notes, the writer records the essence of the information, freeing their mind from having to recall everything.

— From Wikipedia, the free encyclopedia

While any text editor can be used to take notes, the point is doing it in such a way that notes can be easily navigated and organized afterwards.

• Zim A Desktop Wiki that's also an outliner; quirky but friendly, and very flexible. Among the most popular apps here.

Web-based

• TiddlyWiki a non-linear personal web notebook
• Feather Wiki like TiddlyWiki but with the smallest file size possible
• Domino a tool for collaging thoughts

Hosted services:

• rwtxt: "store any text online for easy sharing"
• standard definition notes, "Maybe the world's easiest website maker?"

Mobile

• Markor Markdown Editor, todo.txt, Android app
• Tiddloid an app to work with locally stored TiddlyWikis
• jtx Board journals, notes & tasks for Android | iCalendar compliant | CalDAV sync through DAVx5

Also there's a set of mobile apps for taking notes that all seem to work the same way, and only differ in the amount of features they offer. All are open source and available on F-Droid. Does this have a name?

• Notally
• Another Notes App
• Quillpad

They all seem based on a grid of brief text notes mixed with to-do lists; any of them can have a title, tags and so on, depending. They can be pinned, too. The concept works best with larger screens.

They look similar to Carnet, a large multiplatform app.

Links

• Digital Gardening Tools and Resources
• Awesome Knowledge Management

This page lists lesser known or related apps, so as to keep the main sections clean.

Outliners, note-taking apps or other software with similar uses belong here.

Outliners

• GJots2 and FeatherNotes are two small outliners available in Debian that save their notebooks to single files, in proprietary (if text-based) formats. Both are clunky and limited:
• GJots2 treats notes as plain text but its own file format is human-readable;
• FeatherNotes has a rich text editor (with few options), but no data export.
• OutWiker is a mix between outliners and wikis (see below), running on the desktop. Looks very similar to Zim, except for the lack of a rich text editor. Via @bouncepaw.

Using common formats

The big problem with most outliners is that they insist on using their own ad-hoc file formats instead of common options. This author's outliners are a reaction to this trend:

• Scrunch Edit, a two-pane outliner for Markdown and org files; treats both as plain text (apart from headings);
• OutNoted, an outline note-taking editor; can use org files, Markdown or OPML, but only in specific ways.

A few mobile outliners use org files as well.

Wikis

• Wiki engines like Feather Wiki and Pepperminty Wiki can show a tree of pages in the sidebar, thus acting much like outliners. These two also use Markdown as it happens.

Text User Interface

It's hard to find good apps in this category, because most use a command line, which misses the point.

• TUI Journal Your journal app if you live in a terminal
• JourNote: this author's own take on the matter.
• Mayhem A minimal TUI based task tracker

Old

• Tomboy was once the note-taking app, but it fell from grace as Linux distributions dropped Mono one by one. It was later remade in C++ as Gnote, but most users had moved on.

Potential

• Twine might be good for taking notes
• Collage website makers like HotGlue or Multiverse could work too
• So could Shaarli, a bookmark manager that supports notes with Markdown and tags
• Decker also supports text, images, tables and at least two different ways to link between cards

Links

• An outliner done right: this author's review of TreeLine
• The outline of a game an opinion piece, also by this author

// Render with twopi; neato output looks better, but is too sprawling.
// Also twopi better preserves the original intent. 
digraph {
	layout=twopi
	overlap=scale
	label="Outliners, note-taking apps and everything\nCC-BY-SA"
	
	Outliners [shape=folder;style="bold,filled";fillcolor=yellow]
	Outliners -> { OrgMode Zim }
	OrgMode [fontcolor=blue,label="Org Mode",href="https://orgmode.org/"]
	Outliners -> Old -> hnb
	Old [shape=folder,style=bold]
	Outliners -> Unusual -> { TreeSheets TreeLine }
	TreeSheets [fontcolor=blue,href="https://strlen.com/treesheets/"]
	TreeLine [fontcolor=blue,href="https://treeline.bellz.org/"]
	Unusual [shape=folder,style=bold]
	Outliners -> Mobile -> Orgzly
	Orgzly [ fontcolor=blue, href="https://orgzly.com/" ]
	Mobile [shape=folder,style=bold]
	Outliners -> Formats -> { OrgFiles OPML }
	Formats [shape=folder,style=bold]
	OPML [ fontcolor=blue, href="http://opml.org/" ]
	// Orgzly -> OrgFiles [weight=0]
	OrgFiles [label="Org files"]

	NoteTaking [shape=folder;style="bold,filled";
		fillcolor=yellow;label="Note\nTaking\nApps"]
	NoteTaking -> Zim
	NoteTaking -> Web -> { TiddlyWiki "Feather Wiki" Domino }
	Web [shape=folder,style=bold]
	TiddlyWiki [ fontcolor=blue, href="https://tiddlywiki.com/" ]
	"Feather Wiki" [ fontcolor=blue, href="https://feather.wiki/" ]
	Domino [ fontcolor=blue, href="https://kool.tools/domino/#0,0" ]
	Zim [ fontcolor=blue, href="https://zim-wiki.org/" ]
	NoteTaking -> MobNote -> { Markor Tiddloid }
	Markor [fontcolor=blue,href="https://gsantner.net/project/markor.html"]
	Tiddloid [fontcolor=blue,href="https://github.com/donmor/Tiddloid"]
	MobNote [shape=folder,style=bold,label=Mobile]
	NoteTaking -> OldNote -> { Tomboy Gnote }
	OldNote [label=Old,shape=folder,style=bold]
}