Learn
The ideas behind linked note-taking
These pages explain the concepts rather than the product: what a second brain is and what one actually needs, how a Zettelkasten works and which parts of it were a workaround for paper, what a knowledge graph shows you that search cannot, and how to choose a note-taking app you will still be using in five years.
Written to be useful without the product
Every page here would still be worth reading if Nodum did not exist. That is a deliberate constraint: a guide whose real argument is "and this is why you should buy our thing" teaches nothing, and a reader can tell within a paragraph.
Where Nodum is relevant, it appears at the end of a section as one implementation among several — usually alongside Obsidian, Logseq or Notion, because those are what most people are actually choosing between. The comparison pages handle that argument properly.
The guides
- What a second brain actually isA second brain is an external system for the things you don't want to re-derive. Here's what one needs, and how to build one in an open-source app you own.Second brain
- AI note-taking that reads your own notesMost AI note apps rent you a model and keep your notes. Nodum runs an AI assistant over your own vault, on your own API key, in open-source software.AI notes
- Open-source note-taking: what the licence actually buys youOpen source means the software outlives the company. Here is what to check, which open-source note apps are genuinely open, and where each one fits.Open source
- How to choose a note-taking app you will still be using in five yearsEvery note-taking app demos well. The ones that last get four things right: capture speed, linking, plain-text ownership and a real export. A buyer's guide.Choosing a tool
- What a knowledge graph of your notes actually shows youA note graph is not decoration. It shows clusters you didn't plan, orphans you forgot, and the gaps between the things you know. How to read one, and use it.The graph
- Backlinks and wikilinks: the mechanic that turns notes into a systemA wikilink is what you type. A backlink is what you get for free. Here's how bidirectional linking works, why it changes note-taking, and the syntax.Links
- Zettelkasten, without the mystiqueLuhmann's slip-box in plain terms: atomic notes in your own words, linked to each other, with an entry point. What survives the move to software, and what doesn't.Method
- Personal knowledge management, minus the productivity theatrePKM is capture, connect, retrieve. Most systems fail at the connecting step. A practical guide to the methods, the tools, and what actually matters.PKM
- Self-hosted notes: what it costs, what it buys, and how to run oneSelf-hosting your notes means no vendor, no seat pricing and no exit risk — in exchange for a server you maintain. What it takes, and how Nodum deploys.Self-hosting
- Why notes should be markdown filesMarkdown is the only note format with a demonstrated multi-decade shelf life. What it does well, where it breaks down, and what a good markdown editor gives you.Markdown
Questions people ask
Where should I start with personal knowledge management?
Start by writing notes, not by designing a system. Pick a tool with cheap linking and a real export, title each note as the claim it makes, and link notes together as you notice connections. Structure emerges from the links after a few hundred notes; a hierarchy designed on day one almost never survives.
What is the difference between a second brain and a Zettelkasten?
A Zettelkasten is one specific method for building a second brain: atomic notes written in your own words and linked to each other rather than filed by topic. Second brain is the broader term and covers methods like PARA that organise by actionability instead. Both depend on linking being cheap.
Related reading
Start tying things together.
A vault takes about ten seconds to make. Bring notes with you, or start with one.