This document captures the **nuances, limitations,** and **caveats** of Obsidian tags, focusing on special characters and how Obsidian sorts and parses tags. It also includes references to community feature requests and known workarounds. --- ## 1. Overview of Tag Constraints - **Obsidian tags** must start with `#` and can contain **letters, numbers, underscores, and many Unicode characters.** - They **cannot** contain spaces, commas, or the more “special” punctuation typical in Markdown (e.g., `@`, `.`, `?`, `:`). - **Periods (`.`)** are particularly problematic because they break the tag at the period. - **Slash `/`** is allowed but triggers **nested/hierarchical tags** in Obsidian’s tag pane. (e.g., `#food/fruits/apple` is a nested tag.) In other words, Obsidian “stops” parsing a tag once it encounters disallowed punctuation. Many of these design choices stem from wanting to avoid collisions with Markdown syntax and from how tags are typically parsed by other note-taking apps. --- ## 2. Why Are Certain Characters Disallowed? 1. **Markdown Conflicts:** Characters like `@`, `:` and especially `.` or `\` can conflict with existing Markdown features (links, headings, image syntax, etc.). 2. **Parsing Ambiguity:** Obsidian needs to know when a tag begins and ends. Allowing full punctuation can lead to tricky edge cases (e.g., `#some.tag` might appear like `#some` plus text `.tag`). 3. **Backward Compatibility & Ecosystem:** Some community plugins assume certain delimiters. Expanding the character set can break or complicate plugin code. 4. **User Expectation (Hashtag Conventions):** Many “hashtag” systems do not allow a period or more exotic punctuation. So Obsidian’s devs align with that general standard. --- ## 3. Supported vs. Unsupported Characters ### Commonly **Supported** for Tags - Letters: `a–z`, `A–Z` - Numbers: `0–9` - Underscore: `_` - Hyphen: `-` - Slashes: `/` (for nested tags) - Many **emojis** and extended **Unicode characters** are allowed ### Commonly **Not Supported** for Tags - **Period** (`.`) - **Colon** (`:`) - **Semicolon** (`;`) - **Comma** (`,`) - **Question mark** (`?`) - **Exclamation mark** (`!`) - **At symbol** (`@`) - **Reserved OS path characters** such as `\` on Windows > **Note**: The exact set of disallowed characters can be gleaned from Obsidian’s parser. If Obsidian sees them as “end-of-tag” punctuation, the tag breaks there. --- ## 4. Workarounds for Unsupported Characters Since “.” and certain other punctuation are off-limits, the community and Obsidian support have recommended several **alternative approaches**. Pick whichever suits your workflow best: ### 4.1 Replace With Unicode “Look-alikes” If you truly **must** have an ampersand, slash, or period shape in your tag, you can: - Use **fullwidth** or **Unicode** equivalents: - For `&`: `＆` (U+FF06 Fullwidth Ampersand) - For `.`: `．` (U+FF0E Fullwidth Full Stop) - For `@`: `＠` (U+FF20 Fullwidth Commercial At) - Pros: - Visually similar to the ASCII character. - Cons: - Harder to type or remember, might cause confusion with search or plugin usage. ### 4.2 Nested Tags Instead of Periods Since a period is frequently used to **denote subcategories** (e.g., `#version.1.4.2`), you can replicate that nesting via slashes: arduino CopyEdit `#version/1/4/2` - Pros: - Obsidian’s **tag pane** gives you a nice hierarchy. - Searching is straightforward: `tag:#version/1/4/2`. - Cons: - Each sub-level becomes its own nested tag. You can’t treat `#version/1` and `#version/1/4` as exactly the same entity. ### 4.3 Use Properties or Frontmatter If you need the notion of a semver or “tag with punctuation,” you can instead use **YAML frontmatter** or the **Properties UI** in Obsidian: yaml CopyEdit `--- version: 1.4.2 category: my.software ---` - Then query with [Dataview](https://github.com/blacksmithgu/obsidian-dataview) or the built-in Properties. - Pros: - Perfect for structured data (like versioning or DOIs). - Cons: - Not as convenient to filter in Obsidian’s built-in **Tag Pane**—you’ll need Dataview or advanced search. ### 4.4 Convert Tags to Note Links Another approach is to treat “tags” as **wiki links** to dedicated notes: - Example: Instead of `#g.skill`, you do `[[tag.g.skill]]`, a note titled `tag.g.skill.md`. - You can store these “tag notes” in a `Tags` folder and then link to them anywhere. - Pros: - You can use **any** punctuation in a filename that Windows/your OS allows (besides `\ / : * ? " < > |`). - Great for extremely robust “tag pages” (like MOCs). - Cons: - They no longer appear in the Tag Pane. Searching them is more like searching links. ### 4.5 Embrace Hyphens and Underscores A simpler alternative is to just **replace periods** with `-` or `_`, e.g. `#version_1_4_2`. - Pros: - Easiest to remember/type (no Unicode look-alike). - Plays nicely with typical coding or “snake-case” conventions. - Cons: - Visually less “semantic” if you specifically want a dot or slash. --- ## 5. Sorting & Collation Details Obsidian sorts folders/files/tags using **Chromium’s `Intl.Collator`** JavaScript API. This means: - Sorting can differ slightly from **Windows File Explorer** or your OS’s default. - Unicode has extensive rules about accent marks, numeric sorting, etc. - If you rely on a custom locale, you may see differences in alphabetical order. #### Key Points on Sorting - Typically, numbers (`0–9`) are sorted before letters in ASCII-based ordering. - Fullwidth characters may appear at unexpected positions. - Slashes cause hierarchical grouping in the **tag pane** specifically (not purely alphabetical). --- ## 6. Examples of Structured Tag Systems 1. **Nested Approach (Slashes)** - `#project/alpha`, `#project/beta` - `#version/1/4/2` for semver references - `#people/john_smith` for a person 2. **Status Approach (Underscores)** - `#todo_open`, `#todo_inProgress`, `#todo_done` - `#draft_wip`, `#draft_final` 3. **Emoji Prefixing** - `#📌pin`, `#⚠urgent`, `#✨idea` - Offers quick visual scanning in the tag pane. 4. **Hybrid** - `#people/john_smith` + `#role_developer` + `#🚀growth` - Combining nested tags, underscores, and emojis as needed. --- ## 7. References & Forum Discussions 1. **Official Help Docs** - Obsidian Tags 2. **Feature Requests** - _“[Support special characters (like `.`, `@`) in tags](https://forum.obsidian.md/t/support-special-characters-in-tags-etc/71870)”_ - _“Request to allow periods for semver (`#v1.2.3`)”_ 3. **Sorting Quirks** - _[File order in Obsidian different from Windows File Explorer](https://forum.obsidian.md/t/file-order-in-obsidian-different-from-windows-file-explorer/93480)_ - _[Alphabetic sort depends on `Intl.Collator` (Chromium) locale settings](https://forum.obsidian.md/t/alphabetic-sort-order-should-be-dependent-on-system-input-language/11149)_ 4. **Community Workarounds** - Nested tags plugin: [obsidian-graph-nested-tags](https://github.com/drPilman/obsidian-graph-nested-tags) - Using frontmatter or Dataview properties for DOIs / semver - Replacing `.` with `_` or `-`, or using fullwidth `．` --- ## Conclusion Because **Obsidian tags** are designed to remain compatible with standard hashtag conventions, many special punctuation characters (periods, `@`, `:`) are treated as the **end** of a tag. While this **limits** certain naming schemes (like `#v1.2.3`), the community has devised **several workarounds**: - Use **slashes** for nesting - Swap special symbols with underscores or **fullwidth Unicode** equivalents - Store version/dois in **frontmatter** or **wiki links** - Adopt a more flexible approach to tag naming (snake_case, hyphen-case, etc.) Ultimately, how you handle these constraints will depend on your **workflow**, **search habits**, and **automation** needs. This reference aims to clarify the **“why”** behind these limitations and to provide workable solutions so you can build an **efficient** and **sustainable** tag system in Obsidian.