How to Structure Notes — Categories, Tags, and Folders

[Moy]

This article stems from my previous reflections on the three organizational structures of “categories, tags, and folders.”
I’ve reorganized and shared these thoughts as a sort of interim summary.

Introduction to the Three Organizational Structures

• Category
  In Obsidian, categories are typically implemented through standalone category notes. Each category is an independent note, and other notes establish their belonging relationship by pointing to the corresponding category note via metadata (YAML frontmatter) using bidirectional links (e.g., category: [[Games]]).

This usage comes from Kepano’s example vault. For details, see: How I use Obsidian — Steph Ango

• Tag
  Tags are flat, non-hierarchical metadata markers. A piece of content can have multiple tags, and tags have no parent-child relationships. They are suitable for expressing attributes, states, or lateral associations of content. Examples: #Methodology, #Tools, #ToBeOrganized.

• Folder
  Folders are physical storage structures that determine the actual location of files on the hard drive. Folders can be nested to form a tree-like structure, but they are primarily used for managing file storage and retrieval, not for directly expressing semantic relationships.

Use Case Examples

Taking the same note “Hollow Knight” as an example, here’s how the three organizational structures can be implemented:

• Category Usage
  In the metadata of “Hollow Knight.md,” use a bidirectional link to point to the category note to establish belonging:

  ---  
  category: [[Games]]  
  ---  
  

  Here, “Games” itself is an independent category note that can aggregate all content belonging to this category. With plugins like Dataview or the upcoming core Bases plugin, you can quickly display all sub-notes under this category.

• Tag Usage
  Add tags to the note to express attributes or lateral relationships: Simply type #Games/Masterpiece in the body.

  This allows for quick retrieval of all “masterpiece games.”
  The advantage of tags is their flexibility—you can insert them anywhere in the text.
  However, they can also be more “chaotic” and “scattered” because all your tags are mixed together, and their meanings can vary widely.

• Folder Usage
  Archive notes via physical paths, such as placing “Hollow Knight.md” in the following folder structure:

  Games/  
    Hollow Knight.md  
  

  This method expresses belonging through folders but lacks the ability for multiple belonging and flexible queries.

Basic Comparison

	Category	Tags	Folder
Unique?	Supports multiple	Supports multiple	Unique
Hierarchy	Builds hierarchy via note properties	Supports #a/b hierarchy	Single-level hierarchy
Storage Form	Metadata (specific property with bidirectional links)	Metadata (tags) or inline in text	Physical file path
Query Method	["categories":xx]	tag: #xx	path:xx
Description Note	Bidirectional link to “category note”	None (can manually establish relationships)	FolderNote (folder-specific note)
Semantic Expression	Strong (can use property names to denote relationships, plus category notes can add explanations)	Moderate (requires personal understanding of tag meanings)	Weak
Example	categories: [[People]], [[Artists]]	tags: #people #authors	3-Resource/Archives
Theoretical Quantity	Moderate (only create necessary categories)	Can be numerous, even more than notes (low creation cost, the “freest” option)	Keep minimal to avoid overly complex file structures
Precision	Broad categories	Theoretically the most precise and detailed (highest match accuracy)	Broadest (may lack type meaning, e.g., date-based directories)

• Categories use metadata with bidirectional links to establish belonging, suitable for expressing “what something belongs to,” and support multiple belonging and flexible queries.
• Tags emphasize content attributes and lateral associations, suitable for expressing “what features something has.”
• Folders emphasize physical storage and management, suitable for expressing “where something is stored” (the weakest relationship among the three).

Category notes naturally support additional explanations or specific conditions for displaying sub-notes.
Conversely, tags can achieve similar functionality by manually creating a “tag description note” with the same name as the tag, though this is more cumbersome.

Another advantage of using categories is that in the knowledge graph (Graph), you can clearly see how different notes under the same category point to a central node.

Graph displayed using ExtendedGraph

Of course, displaying tags on the graph can achieve a similar effect, but tags feel more chaotic to me (numerous and broadly expressive). I prefer the controlled organization of category notes.
There are also specific plugins that can make folders appear on the graph.

This also shows that, most of the time, “tags” and “categories” can substitute for each other. Both can implement some features of the other, with the only difference being the level of effort required.
(The folder structure, due to its “single correspondence” limitation, often cannot replicate the features of the other two.)

Key Differences

Here are two critical differences.

I. Decoupling

Compared to categories, tags are more tightly coupled.

This mainly refers to “how much is affected when a change occurs.”

If a tag is modified, all instances of the tag need to be updated.
For example, Chongqing was originally part of Sichuan:
#location/China/Sichuan/Chongqing

When Chongqing became a municipality directly under the central government, it needed to be changed to:
#location/China/Chongqing

Renaming the tag would cause all files using this tag to be updated.

For category notes, only the province property of the Chongqing note changes from [[Sichuan]] to [[Directly-Administered Municipality]]. All notes originally with city: [[Chongqing]] remain unchanged.

II. Precision

As mentioned earlier, tags are overly broad.

For example, take the same category note [[Movies]]:

• For a movie note, category: [[Movies]] means this is a movie.
• For a study about a movie, topic: [[Movies]] means its theme is movies.
• Even when recording a friend who loves movies, hobby: [[Movies]] means their interest is watching movies.

This is an advantage of categories: they can specify the type of relationship.

For tags, you can only have tags: #Movies, which conveys only “relevance” without specifying “how it is relevant.”

---

Since I also use the #Games tag in my daily notes, searching yields many “irrelevant” results.
Unless tags are specifically structured as Type/Games, it’s harder to distinguish “notes about games as a type.”

If you argue, “Tags can also use nested hierarchies to express relationships?”

For example, Type/Games for game-related notes, Topic/Games for studies about games…
This leads to the “chaos” problem—the same Games would be scattered across multiple sub-tags, and searching for #Games wouldn’t even find them.

Summary

Categories, tags, and folders each have their focus. In practice, they can be combined:

• Use categories (category notes + metadata bidirectional links) to organize the knowledge system, ensuring clarity and flexibility.
• Use tags to supplement attributes and lateral associations, improving retrieval efficiency.
• Use folders to manage physical files, facilitating archiving and migration.

Taking “Hollow Knight” as an example, my current approach is:

Create a dedicated “Games Database” folder, placing all game notes inside.
“Hollow Knight” points to the [[Games]] note, allowing all games to be displayed via backlinks.

It can also include statuses like completion time and playtime.

Finally, for further classification (e.g., “Masterpiece” or “Dropped”), tags are most suitable.

The original motivation for this article was learning about the category note structure and wanting to explore its relationship and differences with tags, as well as when each is appropriate.
After research and discussions with peers, I’ve arrived at this interim conclusion.

After using this system for a while, I feel it’s truly the most suitable organizational form for bidirectional-linked notes—arguably unique to them. I highly recommend interested users—especially those with specific requirements for note organization—to give it a try.

That’s all.

[digitaldoctors]

Query Method - tags and categories, you have to search your entire vault. Folders - you don’t need a query - all my tasks are in the Tasks folder.

syncing and sharing - it’s not done by tags or categories … you have two choices: entire vault, or a folder.

Folders are still useful. Especially if certain content doesn’t have much to do with other content.

[Moy]

@digitaldoctors

Query Method - tags and categories, you have to search your entire vault. Folders - you don’t need a query - all my tasks are in the Tasks folder.

Regarding query, actually I’d normally combine them — tags/properties and folders can all serve as filters. Using them together yields the best results.

@digitaldoctors

Folders are still useful. Especially if certain content doesn’t have much to do with other content.

Indeed, and it’s partically impossible to completely avoid using folders

Although Kepano himself has largely abandoned the folder structure - most of his notes are stored in a single folder without furthur hierarchy - in practice, having too many files in one folder can cause performance issues.

[JennyB]

I use Lost Paul’s folder notes quite extensively, which works very well when I have new files set by default to be created in the same folder as the current file.
I may start by making a note about a broad category, and add references and ideas and then when it becomes to large or I need to store supporting material, I convert it into a folder note, and the addition becomes a linked note in the same folder.

So a folder note naturally evolves into both a Map of Content (for the notes created directly from it) and a category note (for any external note that references it).

Is there a way to have the graph view so that I could select any/all folder notes and hide/reveal links that are solely internal to their folders?

[mdbraber]

What I can’t really figure out with @kepano’s vault is when he’s using tags? Often tags are similar to categories - but sometimes they’re different. E.g. a [[People]] category but a musician tag - why not have them both as categories?

[Moy]

Actually I had the same question - and I asked him. Here’s his reply:

I use links more than tags, the tags are partially vestigial.
― A question regarding Category and Tags

So I guess for now he would basically use categories rather than tags. Regarding this example:

E.g. a [[People]] category but a musician tag - why not have them both as categories?

His answer might be: “Yes, you can use both [[People]] and [[Musician]] as categories”

---

But from my personal practice, I’ve concluded that I decide by granularity - the number of tags would be much greater than categories.

You can use tags more freely since creating new tags obviously has lower overhead than creating new categories.
So I would add categories: [[Game]] to all game-related notes, but nothing more.

For more specific classifications like game genres, I would use tags:
#games/RPG, #games/AVG, #games/favorite or #games/masterpiece.

If I cared enough about game genres, it might be worth maintaining categories like category: [[RPG Games]]. But since I don’t need that level of structure yet, tags are sufficient.
(Also, when compiling statistics on the [[Games]] page, you can use tags as filters.)

---

So my personal conclusion is to make full use of their different characteristics:

• Categories are more structured, explicit, and controlled, so I’d create them sparingly for content that truly needs separate classification
  • In other words, if I were a film enthusiast, I might create very detailed movie genre categories… But as a casual viewer who occasionally watches movies, just [[Movies]] would suffice
• Tags are more scattered, lower-cost, and messier (which can be good) - so I use them more freely
  • Practically speaking, you can’t create categories for everything that needs tagging - like my #revisit-later tag wouldn’t work well as a category

Ultimately, these structures are fluid.
When I dive deep enough into a subject and accumulate enough notes to warrant more granular organization, I can always convert relevant tags into more structured categories.

Just like @kepano said:

Having a consistent style collapses hundreds of future decisions into one, and gives me focus. For example, I always pluralize tags so I never have to wonder what to name new tags. Choose rules that feel comfortable to you and write them down. Make your own style guide. You can always change your rules later.
― How I use Obsidian — Steph Ango

[Moy]

Yes, I use almost exactly the same approach (notes → gradually expanding → FolderNote with nested sub-notes), which is fantastic!

Is there a way to have the graph view so that I could select any/all folder notes and hide/reveal links that are solely internal to their folders?

Regarding your question—
Perhaps you could add specific tags (like #folder-note) to all your foldernotes for filtering?

Additionally, I’d recommend the Extended Graph plugin. It allows you to filter notes displayed on the Graph based on links and properties. This way, you can first filter your Foldernotes by tag, then use connection-based filters to show/hide related notes.