Note #5 - An Example Johnny Decimal Index (Mine)

Posted on Sat 07 March 2026 in notes

In Note #4 I mentioned that I was adopting the Johnny Decimal system for organizing my notes. So far this has gone well, and if it continues to be successful I will extend this system to cover other resources besides notes, as the manual suggests.

I'm sharing this index in hopes that it will be a useful example for you to create your own system. I didn't include my index in the previous post for two reasons:

  1. At the time of writing, I still wanted to organize the admin section of my notes.
  2. As we'll see, a full explanation of an index would have risked making that note solely about Johnny Decimal.

As I mentioned in Note #4, the main drawback of Johnny Decimal is the upfront time investment in discovering categories. I had false starts in both my 'Projects' and 'Admin' areas by making categories too narrow, but I later got around this by combining various categories to bring them down to a smaller number.

Without further ado, here is the index. I only provide a few examples on the ID level because some IDs are sensitive and the general structure is probably unique to me. I also don't include zero indexes because these follow the standard JD structure and are therefore uninteresting.

- 00.00 Index
- 10-19 Creative
  - 11 Projects
    - 11.11 Project Kanban
    - 11.13 Creative Writing
    - 11.17 Writing Kanban
    - 11.21 Homelab
  - 12 Media
    - 12.11 Quotes and Excerpts
    - 12.12 Reading
    - 12.13 Video Games
    - 12.14 Video
  - 13 Beliefs
    - 13.11 Philosophy
    - 13.12 Cultural Theory
    - 13.13 Reflections
  - 14 Strategy
    - 14.11 Business Ideas
    - 14.12 Memos and Briefs
- 20-29 Admin
  - 21 Journal
  - 22 Travel and Planning
  - 23 Work
  - 24 Home + Family
  - 25 Money
- 30-39 References and Research
  - 31 Technology and Computer Science
  - 32 Knowledge Management
  - 33 Languages and Linguistics
  - 34 Mathematics and Logic
  - 35 Crafts
  - 36 Philosophy and Religion

Okay, I lied about zero indexes: I included 00.00 Index. This is a markdown file which looks very similar to this note, but with more laconic narration. I'm using the single-file JDex system to organize my categories without the burden of moving real files around. (To be honest, it's not that much of a burden, because I use oil.nvim)

Here is a brief explanation of each category and a few observations.

10-19 Creative

'Creative' is defined very broadly to make it a useful area classification. It includes mostly things I create as well as what would often be called humanities.

11 Projects

Self-explanatory. This stores the projects that I am working on and information relating to each of them. 11.11 Project Kanban uses plainban to record ideas and progress. I also use plainban for tracking the progress of different articles in 11.17 Writing Kanban

12 Media

This stores details of my media consumption such as my reading journal, video games I might have an interest in playing, movies and TV series, etc.

13 Beliefs

This stores my personal beliefs about topics such as philosophy and religion. This should be distinguished from the material in 30-39 References and Research, which is more objective and focused on other people's beliefs.

The most interesting category in here is probably 13.13 Reflections. Before I reorganized using the JD system, this was stored under journal/personal, but the ambiguity that this introduces is a big problem.

What is a journal? Is it a daily logbook or a space for personal reflections, or both? This is a problem because I probably want to look back at my reflections, but I don't care so much to look at which chores I did on such-and-such a date.

To overcome this problem, I separated the two into completely different areas of the index.

14 Strategy

This contains creative thoughts about business, operations concepts, project management, finance and so on. It's for material about administration rather than material used for administration, which is stored in 20-29. The most representative category is probably 14.12 Memos and Briefs, which has high-level (strategic, natch) planning for various business and administrative tasks I need to do.

Once a project crosses from 'should I do this?' and 'what am I doing?' to 'which tasks need to be performed?' it can happily move across to 20-29.

20-29 Admin

The admin area is about things that happen in the real world. Groceries, finances, travel plans and all that.

The largest category by far is 21 Journal, which contains every daily, weekly, monthly, and yearly note I've created since 2023. Because this is a very large category - and has inherent chronological organization using daily-notes.nvim - I deviated from the Johnny Decimal system to create my own structure, which looks like this:

- 21 Journal
  - 2023 (YYYY)
    - daily
      - 2023-01-01.md (YYYY-MM-DD)
    - monthly
      - 2023-01.md (YYYY-MM)
    - weekly
      - 2023-week-01.md (YYYY-week-WW)
    - 2023.md (YYYY)

Note that this type of deviation is actually accounted for in 11.06 of the Johnny Decimal guide.

I prefer this type of layout to the common YYYY/MM/DD.md structure for two reasons:

  1. It provides a space for week-of-year notes, which follow a different format to what the typical nested scheme implies.
  2. It separates notes by type instead of date as such. Notes for a day inherently have a different structure to notes for a week, and plans for a quarter or a year are likely to be even more high-level. In fact, The 7 Habits of Highly Effective People argues against using daily notes at all.

Since the other categories in Admin are self-explanatory, I won't go into more depth here.

30-39 References and Research

This is a category that's designed for holding in-depth information such as course notes, lists of learning materials, and web clippings. Note that I don't divide my notes by the traditional academic schools or faculties (humanities, sciences, arts, etc). There are two reasons for this:

First, it's unlikely that I'm really interested in more than 9 broad categories; even developing a full systematic philosophy reference would easily exceed Johnny Decimal's soft limit of 99 IDs.

Second, I've always been very interdisciplinary, and oppose separating STEM from the arts. Many interesting connections come about by having dialogue and relationships between different subjects. In fact, I might re-organize these categories in the future to deliberately mix together technology and arts topics.

What is a bit puzzling about this area is where exactly it starts and ends. An accounting textbook clearly lives here. But what about my notes on how to use beancount, which could feasibly live here, in 25 Money, or even in 14 Strategy?

I think this will probably be something that needs to be decided on a case-by-case basis and recorded in a decision log - perhaps as part of the index itself. This is part of the Librarian role described on the Johnny Decimal website, and seems like a useful complement to the system itself.

Final Thoughts

Johnny Decimal is a smooth character, and I find he insinuates himself into parts of my file system I didn't expect.

I reorganized my work notes and found that it becomes natural to stash release artifacts alongside release notes, which I would not do without a filing system.

For now, at least, the JD system has helped tame some of my chaotic excesses and irresponsibility in managing knowledge and data.