Obsidian Bases Skill

When to Use

• Use when creating or editing .base files in Obsidian.
• Use for database-like note views with filters, formulas, summaries, or cards/tables.
• Use when the user asks about Obsidian Bases specifically.

Workflow

1. Create the file: Create a .base file in the vault with valid YAML content
2. Define scope: Add filters to select which notes appear (by tag, folder, property, or date)
3. Add formulas (optional): Define computed properties in the formulas section
4. Configure views: Add one or more views (table, cards, list, or map) with order specifying which properties to display
5. Validate: Verify the file is valid YAML with no syntax errors. Check that all referenced properties and formulas exist. Common issues: unquoted strings containing special YAML characters, mismatched quotes in formula expressions, referencing formula.X without defining X in formulas
6. Test in Obsidian: Open the .base file in Obsidian to confirm the view renders correctly. If it shows a YAML error, check quoting rules below

Schema

Base files use the .base extension and contain valid YAML.

# Global filters apply to ALL views in the base
filters:
  # Can be a single filter string
  # OR a recursive filter object with and/or/not
  and: []
  or: []
  not: []

# Define formula properties that can be used across all views
formulas:
  formula_name: 'expression'

# Configure display names and settings for properties
properties:
  property_name:
    displayName: "Display Name"
  formula.formula_name:
    displayName: "Formula Display Name"
  file.ext:
    displayName: "Extension"

# Define custom summary formulas
summaries:
  custom_summary_name: 'values.mean().round(3)'

# Define one or more views
views:
  - type: table | cards | list | map
    name: "View Name"
    limit: 10                    # Optional: limit results
    groupBy:                     # Optional: group results
      property: property_name
      direction: ASC | DESC
    filters:                     # View-specific filters
      and: []
    order:                       # Properties to display in order
      - file.name
      - property_name
      - formula.formula_name
    summaries:                   # Map properties to summary formulas
      property_name: Average

Filter Syntax

Filters narrow down results. They can be applied globally or per-view.

Filter Structure

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

# AND - all conditions must be true
filters:
  and:
    - 'status == "done"'
    - 'priority > 3'

# OR - any condition can be true
filters:
  or:
    - 'file.hasTag("book")'
    - 'file.hasTag("article")'

# NOT - exclude matching items
filters:
  not:
    - 'file.hasTag("archived")'

# Nested filters
filters:
  or:
    - file.hasTag("tag")
    - and:
        - file.hasTag("book")
        - file.hasLink("Textbook")
    - not:
        - file.hasTag("book")
        - file.inFolder("Required Reading")

Filter Operators

Operator	Description
==	equals
!=	not equal
>	greater than
<	less than
>=	greater than or equal
<=	less than or equal
&&	logical and
\|\|	logical or
<code>!</code>	logical not

Properties

Three Types of Properties

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

Property	Type	Description
file.name	String	File name
file.basename	String	File name without extension
file.path	String	Full path to file
file.folder	String	Parent folder path
file.ext	String	File extension
file.size	Number	File size in bytes
file.ctime	Date	Created time
file.mtime	Date	Modified time
file.tags	List	All tags in file
file.links	List	Internal links in file
file.backlinks	List	Files linking to this file
file.embeds	List	Embeds in the note
file.properties	Object	All frontmatter properties

The this Keyword

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

Formula Syntax

Formulas compute values from properties. Defined in the formulas section.

formulas:
  # Simple arithmetic
  total: "price * quantity"

  # Conditional logic
  status_icon: 'if(done, "✅", "⏳")'

  # String formatting
  formatted_price: 'if(price, price.toFixed(2) + " dollars")'

  # Date formatting
  created: 'file.ctime.format("YYYY-MM-DD")'

  # Calculate days since created (use .days for Duration)
  days_old: '(now() - file.ctime).days'

  # Calculate days until due date
  days_until_due: 'if(due_date, (date(due_date) - today()).days, "")'

Key Functions

Most commonly used functions. For the complete reference of all types (Date, String, Number, List, File, Link, Object, RegExp), see FUNCTIONS_REFERENCE.md.

Function	Signature	Description
date()	date(string): date	Parse string to date (YYYY-MM-DD HH:mm:ss)
now()	now(): date	Current date and time
today()	today(): date	Current date (time = 00:00:00)
if()	if(condition, trueResult, falseResult?)	Conditional
duration()	duration(string): duration	Parse duration string
file()	file(path): file	Get file object
link()	link(path, display?): Link	Create a link

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

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

# CORRECT: Calculate days between dates
"(date(due_date) - today()).days"                    # Returns number of days
"(now() - file.ctime).days"                          # Days since created
"(date(due_date) - today()).days.round(0)"           # Rounded days

# WRONG - will cause error:
# "((date(due) - today()) / 86400000).round(0)"      # Duration doesn't support division then round

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\""       # Tomorrow
"today() + \"7d\""        # A week from today
"now() - file.ctime"      # Returns Duration
"(now() - file.ctime).days"  # Get days as number

View Types

Table View

views:
  - type: table
    name: "My Table"
    order:
      - file.name
      - status
      - due_date
    summaries:
      price: Sum
      count: Average

Cards View

views:
  - type: cards
    name: "Gallery"
    order:
      - file.name
      - cover_image
      - description

List View

views:
  - type: list
    name: "Simple List"
    order:
      - file.name
      - status

Map View

Requires latitude/longitude properties and the Maps community plugin.

views:
  - type: map
    name: "Locations"
    # Map-specific settings for lat/lng properties

Default Summary Formulas

Name	Input Type	Description
Average	Number	Mathematical mean
Min	Number	Smallest number
Max	Number	Largest number
Sum	Number	Sum of all numbers
Range	Number	Max - Min
Median	Number	Mathematical median
Stddev	Number	Standard deviation
Earliest	Date	Earliest date
Latest	Date	Latest date
Range	Date	Latest - Earliest
Checked	Boolean	Count of true values
Unchecked	Boolean	Count of false values
Empty	Any	Count of empty values
Filled	Any	Count of non-empty values
Unique	Any	Count of unique values

Complete 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

Embed in Markdown files:

![[MyBase.base]]

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

YAML Quoting Rules

• Use single quotes for formulas containing double quotes: 'if(done, "Yes", "No")'
• Use double quotes for simple strings: "My View Name"
• Escape nested quotes properly in complex expressions

Troubleshooting

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.

# 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.

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

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

References

• Bases Syntax
• Functions
• Views
• Formulas
• Complete Functions Reference

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.