Johnny.Decimal: give everything you keep a number you can find again

Johnny.Decimal is a system for organizing files, notes and anything else you keep, using short numbers. You divide your life or work into at most ten areas, each area into at most ten categories, and every item in a category gets an ID. The result is a number like 11.21 that tells you exactly where something is, and that you can say out loud, type in a search box or write on a folder.

This guide explains the structure, the reserved "standard zeros", the common mistakes, and how to run Johnny.Decimal in Barside, a free desktop app for Windows, Linux and Mac.

Where Johnny.Decimal comes from

Johnny.Decimal was created by Johnny Noble, and its site now credits Johnny Noble and Lucy Butcher. The about page tells the origin: "Johnny.Decimal was created in 2010 when a bunch of friends and I produced a contemporary dance performance." Since 2023, both work on it full-time.

The system is free. Its site says you can use it "for any purpose, personal or commercial", and the documentation is licensed CC BY-NC-SA 4.0. As the site puts it, "You can make money using Johnny.Decimal; you can't make money selling Johnny.Decimal." Always write the name with the dot.

How Johnny.Decimal is structured

Areas

You get at most ten areas, numbered in ranges: 00-09, 10-19, 20-29 and so on up to 90-99. The site says: "Think of them as 'areas of your life' or 'areas of expertise'." A household might use 10-19 for life admin, 20-29 for work and 30-39 for hobbies.

Categories

Each area holds at most ten categories, numbered within its range: area 10-19 holds categories 10, 11 and so on to 19. The site calls categories "Collections of similar stuff." In life admin, 11 might be money, 12 your home and 13 health.

IDs

Each category holds up to 100 IDs, numbered in the order you create them and written after a dot. 12.14 might be your lease, 13.12 your vaccination records. The item lives at that number, and the number is how you find it.

AC.ID notation

The full address is AC.ID. In the site's words: "The number before the decimal tells us what area and category we're in. The number after the decimal is the ID." So 11.21 is ID 21 in category 11, which sits in area 10-19. If you keep several separate systems, say one for work and one for home, a system code goes in front, as SYS.AC.ID.

The standard zeros

Johnny.Decimal reserves some numbers for running the system itself.

• The area-management category. "Within each area, the category that ends 0 is the area-management category." Category 10 manages area 10-19.
• The reserved IDs. In every category, IDs .00 to .09 are set aside: .00 JDex, .01 Inbox, .02 Task and project management, .03 Templates, .04 Links, .05 AI, .06 to .08 reserved, and .09 Archive.

If you use the standard zeros, your own IDs in each category start after .09. You do not have to use them all; they are there so the same kind of thing always sits at the same number.

Common Johnny.Decimal mistakes

• Too many categories. The site's advice is "Prefer fewer, broader categories". Ten categories per area is a limit, not a target.
• Categories you never work in. "A category is where you work." If you never open a category, merge it into another.
• Designing everything up front. The site says you can build top-down, starting with areas, or bottom-up, starting with categories. Either way, start with what you have and let the system grow.
• Adding more levels. The system has three: area, category and ID. Resist nesting more folders under them, or the short numbers stop telling you where things are.
• Reshuffling numbers. IDs are numbered in order of creation. Renumbering to keep things "tidy" breaks every place you wrote the old number.

How to run Johnny.Decimal in Barside

Barside keeps notes in workspaces, each with its own color, and each note lives in one workspace. Notes can hold text, checklists, tables, links to other notes and files of any kind. That maps onto Johnny.Decimal with little effort.

Areas as workspaces

1. In the sidebar, under Workspaces, press + (New workspace).
2. Name it with its range, like 10-19 Life admin, and pick a color.
3. Repeat for each area. Ten workspaces, the most Johnny.Decimal allows, is still easy to scan.

See workspaces for projects for everything a workspace holds.

IDs as notes

1. In the area's workspace, press Ctrl+N and title the note with its full ID and name, like 12.14 Lease.
2. In the sort menu above your notes, choose Title A–Z. Your IDs line up in number order, category by category.
3. Keep everything for the ID in that one note: text, checklists, a table, pictures. Drag in the files themselves, such as the signed PDF, and they show as cards you can open, with Show in folder and Save a copy.

Categories as index notes

Barside has no folders inside a workspace, so give each category an index note. Title it with the category's .00 ID, like 12.00 Home, which matches the standard zeros. List every ID in it with a link: type [[ and the number, and pick the note. Then open Note options and choose Pin to the top, so your category indexes lead the workspace. The guide to maps of content covers hub notes like these in more depth.

Find anything by its number

Press Alt+Shift+Space in any app, or Ctrl+K in Barside, and type the number, like 12.14. The search bar searches note titles and text, so the ID brings the note up at once. Press Ctrl+D on a result you open often to keep it as a favorite.

The standard zeros in Barside

• .01 Inbox. A note per category for things to file later, or one for the whole area in its 0 category.
• .02 Task and project management. A checklist in that note. Every item shows on the task board, and the board's workspace menu narrows it to one area.
• .03 Templates. Save any note with Note options → Save as template, and name the template with its ID. See note templates.
• .04 Links. Each note has its own bookmark bar, so the .04 note can hold the category's links in named groups.
• .09 Archive. A note per category that links what you retired, so the numbers stay taken.

Files on your disk

Barside does not create folders on your computer's disk. If you also keep a Johnny.Decimal folder tree in your file system or cloud drive, use exactly the same numbers in Barside's note titles. Then 12.14 Lease the note and 12.14 Lease the folder always point to the same thing.

Who Johnny.Decimal suits

• People drowning in documents, like contracts, receipts and records, who need to find a file in seconds.
• Small teams and households that want everyone to say "it's in 12.14" and mean the same place.
• Anyone who likes stable addresses, since an ID does not move when your priorities change.

It suits people less if their work is mostly short projects that come and go, where filing by actionability, as in the PARA method, fits better. Some people combine the two: PARA for active projects, Johnny.Decimal for long-lived records.

Related methods

• The PARA method, Tiago Forte's four groups that move with your projects.
• Maps of content, hub notes that gather a topic, much like a category index.
• Building a Second Brain, a full cycle from capturing to making things.
• The Zettelkasten method, small linked notes with fixed addresses.