If you want to learn something for the long run, you have to write it down. If you want to really understand something, you have to translate it into your own words. (Sönke Ahrens, How to Take Smart Notes)

Zettelkasten is a German word for “slip box.” Made famous by Niklas Luhmann (1927–1998), a Zettelkasten is a tool for thinking and writing. It was initially an analog system for taking notes using index cards and wooden boxes. Some people still prefer the analog approach, yet modern digital tools make a Zettelkasten much less complicated and arguably more powerful.

Niklas Luhmann

Niklas Luhmann (1927–1998) was a German sociologist who was highly productive. He wrote over 70 books and nearly 400 scholarly articles on a variety of topics.

The key to Luhmann’s success was not his ability to sit down on a blank sheet and write a book; instead, it was all about his note-taking system. He developed a simple method to take notes using index cards. His approach was called a Zettelkasten or Slip-Box.

Throughout the day, he would write his Fleeting Notes and Literature Notes in a notebook. Then at night, he takes those ideas and converts them into Permanent Notes on his index cards.

To keep the notes connected and discoverable, Luhmann devised a numbering system. He would give each card a unique number, which allowed cards to be referenced by other cards. In today’s digital world, this could resemble hyperlinks.

Instead of adding a new card to the end of the stack, he would determine if it was related to any previously existing note. He would then add the new card behind the related note and assign it a unique number. For example, if he put the new card behind an existing card that was numbered 57/12, the new card would be numbered 57/13. The next related card would have the number 57/13a. And so on.

Types of Notes

There are several types of notes in a Zettelkasten system, including Fleeting Notes, Literature Notes, Permanent Notes, and Project Notes.

Fleeting Notes

Fleeting Notes are temporary. The primary purpose is to quickly capture ideas, thoughts, feelings, things to do, or anything else that comes to mind that you may want to refer back to at a later time.

These notes should be processed as quickly as possible, typically within a few days, before losing meaning.

They are written in a way that provides just enough information to relay their meaning. It does not need to be grammatically correct. Use abbreviations, shorthand, or whatever you need to capture the information quickly. Even a picture can work at times.

When the note is reviewed, it can either be immediately discarded if it has no more relevance. If worth keeping, create a Permanent Note, then throw the Fleeting Note away. You no longer need it.

Literature Notes

Literature Notes are taken while reading or consuming content from videos, podcasts, or other media. They are more formal than Fleeting Notes but not as formal as Permanent Notes. Short and to the point.

Literature notes are written in your own words. They are your tool for ensuring you understand the concept. Therefore, copy-and-paste will do you no good.

Keep the bibliographic details together with your Literature Notes so that you can quickly get back to the source if you need to review the content again.

It can help write your Literature Notes on paper, forcing you to write in your own words and minimize digital distractions. Also, writing can help you slow down, think, and can even help you remember better.

Permanent Notes

Permanent Notes are what form your knowledge base. They are written entirely in your own words and express your understanding and opinions of a single specific topic.

Use your Literature Notes to form the ideas that go into your Permanent notes. The note itself should be about a single topic. It is atomic. It is written in a way that anyone, including your future self, can understand its meaning.

Your collection of Permanent Notes will be your archive that you can pull from at any time. After accumulating enough notes about a topic, you will find that if you want to write something about that topic, it is as simple as pulling up your ready-to-go Permanent Notes and organizing them into a draft.

Using Bi-Directional Links within your Permanent Notes is an easy way to link your thoughts. You can also use tags.

Keep your references with your note so you can always find the source(s) where you found the ideas.

Project Notes

Project Notes are for a specific project. They include meeting notes, checklists, and miscellaneous notes. Once the project is complete, you will archive them with the project.

Project Notes generally do not contribute to your overall PKM (Personal Knowledge Management). If you have notes that can help multiple projects, convert them into more generic Permanent Notes instead.

Core Principles of a Zettelkasten

The following are what I consider the core principles of a Zettelkasten.

Create one note per idea

Creating one note per idea applies to the Permanent Notes, which I’ll talk more about below. Creating one note for each idea allows the most flexibility. You can then use that one note with other related notes in more ways than you realize. Imagine using index cards for your notes. You can take all of your notes and spread them out on the table. Then you can easily rearrange them, making connections between those notes. You can do the same thing in the digital format; however, your notes need to be atomic to accomplish this.

Give each note a unique ID

When using digital tools, just a unique Title will suffice.

Write your notes in your own words

Doing so helps ensure you understand what you’re consuming. If you can’t write it in your own words, you likely don’t understand it.

Include context with your notes

Write your notes so that anyone, including your future self, can understand them. This is especially helpful if you want to share a specific idea or even combine ideas into an article (like this one).

Connect your notes

The analog method would require you to generate unique identifiers for each note. Digital tools make this much simpler by creating bi-directional links.

Keep the organization of your notes simple

My personal preference is to capture Fleeting Notes and Literature Notes on paper. I then write my Permanent Notes in Obsidian all in one folder.

Suppose you keep all of your notes in one application. In that case, an option is to create a folder for each type of note (Fleeting, Literature, Permanent, Project) and store all of your notes in the appropriate folder without any other subfolders.

When organizing into a hierarchy, we often spend more time than necessary managing our notes rather than creating them.

Let the links and tags in your notes create the hierarchy naturally!

Digital Zettelkasten applications

There is a wide variety of applications that can be used for a digital Zettelkasten. You could use familiar applications like Evernote, Bear, Apple Notes, and OneNote. Still, they lack specific functionality, like bi-directional links, that would take your digital Zettelkasten to the next level.

Several applications are built specifically for a Zettelkasten. These include The Archive and Zettlr, Roam Research, Obsidian, Notion, RemNote, TiddlyWiki, and Amplenote,


I hope this helped explain what a Zettelkasten is and gives you some ideas for using one for your note-taking system. Everyone has different methods that work best for them. I recommend checking out some of the communities where you can find more information and have discussions with others. The Zettelkasten Forum, Obsidian Forum, and Zettelkasten Subreddit are great places to start.


Ahrens, Sönke. How to Take Smart Notes: One Simple Technique to Boost Writing, Learning and Thinking: For Students, Academics and Nonfiction Book Writers. CreateSpace, 2017. Amazon

Wikipedia Contributors. 2020. “Niklas Luhmann.” Wikipedia. Wikimedia Foundation. September 5, 2020. https://en.wikipedia.org/wiki/NiklasLuhmann.

“Communicating with Slip Boxes by Niklas Luhmann.” 2020. Surge.Sh. 2020. http://luhmann.surge.sh/communicating-with-slip-boxes.

sascha. 2020. “Introduction to the Zettelkasten Method Zettelkasten Method.” Zettelkasten.De. October 27, 2020. [zettelkasten.de/introduct...](https://zettelkasten.de/introduction/.)