Obsidian Bases

When to Use

• Use when creating or editing .base files in an Obsidian vault.
• Use for database-like note views with filters, formulas, summaries, or cards/tables.
• Use when the user asks about Obsidian Bases specifically, or mentions .base files, table views, card views, list views, map views, filters, or formulas.
• Use when the user wants to embed a Base in a Markdown note (![[MyBase.base]]).

Prerequisites

• Obsidian installed with Bases support (Obsidian 1.9+ or a build that includes the Bases feature).
• The target vault must be open and accessible on the Windows host (PowerShell).
• For map views, the Maps community plugin must be installed and latitude/longitude properties must exist on the target notes.

Procedure

1. Create the .base file

Create a .base file in the vault using valid YAML. On Windows (PowerShell):

New-Item -Path "C:\path\to\vault\MyBase.base" -ItemType File -Force

Then write YAML content into the file. The entire file must be valid YAML.

2. Define global filters

Add a top-level filters key to select which notes appear across ALL views. Filters can be a single string or a recursive object with and / or / not.

# Single filter string
filters: 'status == "done"'

# Recursive object
filters:
  and:
    - 'status == "done"'
    - 'priority > 3'
  or:
    - 'file.hasTag("book")'
    - 'file.hasTag("article")'
  not:
    - 'file.hasTag("archived")'

3. Define formulas (optional)

Add a formulas section to compute values from properties. Formula expressions are strings.

formulas:
  total: "price * quantity"
  status_icon: 'if(done, "✅", "⏳")'
  days_until_due: 'if(due_date, (date(due_date) - today()).days, "")'

4. Configure property display names (optional)

Use the properties section to set displayName for note properties, file properties, or formula properties.

properties:
  status:
    displayName: "Status"
  formula.days_until_due:
    displayName: "Days Until Due"
  file.ext:
    displayName: "Extension"

5. Define custom summaries (optional)

summaries:
  custom_summary_name: 'values.mean().round(3)'

6. Configure views

Add one or more views under views. Each view has a type (table, cards, list, or map), a name, and an order list specifying which properties to display.

views:
  - type: table
    name: "My Table"
    limit: 10
    groupBy:
      property: status
      direction: ASC
    filters:
      and:
        - 'status != "done"'
    order:
      - file.name
      - status
      - due_date
      - formula.days_until_due
    summaries:
      price: Sum
      formula.days_until_due: Average

7. Validate the YAML

Verify the file is valid YAML with no syntax errors. Check that:

• All referenced formula.X entries in order or properties have a matching definition in formulas.
• All strings containing special YAML characters (:, {, }, [, ], ,, &, *, #, ?, |, -, <, >, =, !, %, @, `) are quoted.
• Formulas containing double quotes are wrapped in single quotes.

On Windows (PowerShell), you can do a quick YAML lint if Python is available:

python -c "import yaml,sys; yaml.safe_load(open(r'C:\path\to\vault\MyBase.base',encoding='utf-8')); print('YAML OK')"

8. Test in Obsidian

Open the .base file in Obsidian to confirm the view renders correctly. If Obsidian shows a YAML error, re-check quoting rules and formula syntax.

Schema Reference

filters:
  and: []
  or: []
  not: []

formulas:
  formula_name: 'expression'

properties:
  property_name:
    displayName: "Display Name"
  formula.formula_name:
    displayName: "Formula Display Name"
  file.ext:
    displayName: "Extension"

summaries:
  custom_summary_name: 'values.mean().round(3)'

views:
  - type: table | cards | list | map
    name: "View Name"
    limit: 10
    groupBy:
      property: property_name
      direction: ASC | DESC
    filters:
      and: []
    order:
      - file.name
      - property_name
      - formula.formula_name
    summaries:
      property_name: Average

Filter Operators

Property Types

1. Note properties — From frontmatter: note.author or just author.
2. File properties — File metadata: file.name, file.mtime, etc.
3. Formula properties — Computed values: formula.my_formula.

File Properties Reference

The this Keyword

• In the main content area: refers to the base file itself.
• When embedded: refers to the embedding file.
• In the sidebar: refers to the active file in main content.

Key Functions

Most commonly used functions. Load references/FUNCTIONS_REFERENCE.md when you need the complete reference for all types (Date, String, Number, List, File, Link, Object, RegExp).

Duration Type

When subtracting two dates, the result is a Duration type (not a number).

Duration Fields: duration.days, duration.hours, duration.minutes, duration.seconds, duration.milliseconds

HARD RULE: Duration does NOT support .round(), .floor(), .ceil() directly. Access a numeric field first (like .days), then apply number functions.

# CORRECT
"(date(due_date) - today()).days"
"(now() - file.ctime).days"
"(date(due_date) - today()).days.round(0)"

# WRONG — will cause error
# "((date(due) - today()) / 86400000).round(0)"
# "(now() - file.ctime).round(0)"

Date Arithmetic

Duration units: y/year/years, M/month/months, d/day/days, w/week/weeks, h/hour/hours, m/minute/minutes, s/second/seconds.

"now() + \"1 day\""
"today() + \"7d\""
"now() - file.ctime"
"(now() - file.ctime).days"

Default Summary Formulas

Examples

Task Tracker Base

filters:
  and:
    - file.hasTag("task")
    - 'file.ext == "md"'

formulas:
  days_until_due: 'if(due, (date(due) - today()).days, "")'
  is_overdue: 'if(due, date(due) < today() && status != "done", false)'
  priority_label: 'if(priority == 1, "🔴 High", if(priority == 2, "🟡 Medium", "🟢 Low"))'

properties:
  status:
    displayName: Status
  formula.days_until_due:
    displayName: "Days Until Due"
  formula.priority_label:
    displayName: Priority

views:
  - type: table
    name: "Active Tasks"
    filters:
      and:
        - 'status != "done"'
    order:
      - file.name
      - status
      - formula.priority_label
      - due
      - formula.days_until_due
    groupBy:
      property: status
      direction: ASC
    summaries:
      formula.days_until_due: Average

  - type: table
    name: "Completed"
    filters:
      and:
        - 'status == "done"'
    order:
      - file.name
      - completed_date

Reading List Base

filters:
  or:
    - file.hasTag("book")
    - file.hasTag("article")

formulas:
  reading_time: 'if(pages, (pages * 2).toString() + " min", "")'
  status_icon: 'if(status == "reading", "📖", if(status == "done", "✅", "📚"))'
  year_read: 'if(finished_date, date(finished_date).year, "")'

properties:
  author:
    displayName: Author
  formula.status_icon:
    displayName: ""
  formula.reading_time:
    displayName: "Est. Time"

views:
  - type: cards
    name: "Library"
    order:
      - cover
      - file.name
      - author
      - formula.status_icon
    filters:
      not:
        - 'status == "dropped"'

  - type: table
    name: "Reading List"
    filters:
      and:
        - 'status == "to-read"'
    order:
      - file.name
      - author
      - pages
      - formula.reading_time

Daily Notes Index

filters:
  and:
    - file.inFolder("Daily Notes")
    - '/^\d{4}-\d{2}-\d{2}$/.matches(file.basename)'

formulas:
  word_estimate: '(file.size / 5).round(0)'
  day_of_week: 'date(file.basename).format("dddd")'

properties:
  formula.day_of_week:
    displayName: "Day"
  formula.word_estimate:
    displayName: "~Words"

views:
  - type: table
    name: "Recent Notes"
    limit: 30
    order:
      - file.name
      - formula.day_of_week
      - formula.word_estimate
      - file.mtime

Embedding Bases in Markdown

![[MyBase.base]]

<!-- Specific view -->
![[MyBase.base#View Name]]

Pitfalls

YAML Syntax Errors

Unquoted special characters: Strings containing :, {, }, [, ], ,, &, *, #, ?, |, -, <, >, =, !, %, @, ` must be quoted.

# WRONG — colon in unquoted string
displayName: Status: Active

# CORRECT
displayName: "Status: Active"

Mismatched quotes in formulas: When a formula contains double quotes, wrap the entire formula in single quotes.

# WRONG — double quotes inside double quotes
formulas:
  label: "if(done, "Yes", "No")"

# CORRECT — single quotes wrapping double quotes
formulas:
  label: 'if(done, "Yes", "No")'

Common Formula Errors

Duration math without field access: Subtracting dates returns a Duration, not a number. Always access .days, .hours, etc. before calling number functions.

# WRONG — Duration is not a number
"(now() - file.ctime).round(0)"

# CORRECT — access .days first, then round
"(now() - file.ctime).days.round(0)"

Missing null checks: Properties may not exist on all notes. Use if() to guard.

# WRONG — crashes if due_date is empty
"(date(due_date) - today()).days"

# CORRECT — guard with if()
'if(due_date, (date(due_date) - today()).days, "")'

Referencing undefined formulas: Ensure every formula.X in order or properties has a matching entry in formulas. Undefined formula references fail silently.

# This will fail silently if 'total' is not defined in formulas
order:
  - formula.total

# Fix: define it
formulas:
  total: "price * quantity"

Verification

1. YAML validity — Run a YAML parse check (if Python is available):

python -c "import yaml; yaml.safe_load(open(r'C:\path\to\vault\MyBase.base',encoding='utf-8')); print('YAML OK')"

Expected output: YAML OK

2. Formula references — Confirm every formula.X referenced in order, properties, or summaries has a matching key in the formulas section.

3. Render check — Open the .base file in Obsidian. The view should render without a YAML error banner. If an error appears, check quoting rules and formula syntax.

4. Embed check — Embed the base in a Markdown note with ![[MyBase.base]] and confirm the view appears inline.

References

• Bases Syntax
• Functions
• Views
• Formulas
• Load references/FUNCTIONS_REFERENCE.md when you need the complete function reference for all types (Date, String, Number, List, File, Link, Object, RegExp).

Limitations

• Use this skill only when the task clearly matches the scope described above.
• Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
• Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.