Variable Fonts Overview

Variable fonts are OpenType fonts that contain multiple variations of a typeface in a single file. Instead of having separate font files for different weights, widths, or styles, a variable font uses variation axes to interpolate between different design extremes.

Key Tables

Table	Description
fvar	Defines variation axes and named instances
gvar	(TrueType) Glyph variation data as delta tuples
CFF2	(OpenType) Variation data as blend operators
avar	(Optional) Axis value mappings for non-linear interpolation
STAT	(Optional) Style attributes and axis value names
HVAR/VVAR/MVAR	(Optional) Metrics variation tables

Variation Axes

Each axis represents a design dimension along which the font can vary.

Common Registered Axes

Tag	Name	Range	Typical Values
wght	Weight	1-1000	400 (Regular) to 700 (Bold)
wdth	Width	1-1000	75 (Condensed) to 125 (Expanded)
slnt	Slant	-90 to 90	Degrees
ital	Italic	0 or 1	0 (Roman), 1 (Italic)
opsz	Optical Size	Varies	Point size for optical sizing

Custom Axes

Custom axes use four-character tags starting with uppercase letter:

• GRAD — Grade
• XOPQ — X-Optical-Size
• YOPQ — Y-Optical-Size
• XTRA — X-Transparency
• And many others...

Named Instances

Variable fonts can define named instances — predefined points in the design space with specific names:

• "Regular"
• "Bold"
• "Light"
• "Condensed Bold"
• "Expanded Italic"

Guides

• Axes & Instances — Working with axes and named instances
• Instance Generation — Generate static fonts from variable fonts
• Format Conversion — Convert variable fonts between formats
• Named Instances — Work with named instances
• Static Fonts — Convert to static fonts
• Advanced Topics — Advanced variable font operations

Quick Start

Get Axis Information

font = Fontisan::FontLoader.load('variable.ttf')
fvar = font.tables['fvar']

fvar.axes.each do |axis|
  puts "#{axis.tag}: #{axis.min_value} - #{axis.max_value}"
end

Generate Instance

# Generate bold instance
fontisan instance variable.ttf --wght 700 --output bold.ttf

# Generate with multiple axes
fontisan instance variable.ttf --wght 700 --wdth 75 --output condensed-bold.ttf