subset

Create font subsets.

Usage

fontisan subset FONT [options]

Arguments

Argument	Description
FONT	Input font file

Options

Option	Description
--chars TEXT	Characters to include
--chars-file PATH	File with characters
--unicodes RANGE	Unicode ranges
--glyphs LIST	Glyph names/IDs
--output PATH	Output file
--output-format FORMAT	Output format
--profile PROFILE	Subsetting profile (pdf, web, minimal, full; default pdf)
--retain-gids	Retain glyph IDs

Examples

By Characters

# Subset to specific characters
fontisan subset font.ttf --chars "ABCDEFabcdef0123456789" --output subset.ttf

# Subset to ASCII
fontisan subset font.ttf --chars "$(printf '%s' {a..z} {A..Z} {0..9})" --output ascii.ttf

By Unicode Range

# Basic Latin only
fontisan subset font.ttf --unicodes "U+0000-007F" --output basic-latin.ttf

# Latin + Latin-1
fontisan subset font.ttf --unicodes "U+0000-00FF" --output latin1.ttf

# Multiple ranges
fontisan subset font.ttf --unicodes "U+0000-007F,U+00A0-00FF" --output extended.ttf

By Glyph Names

# Specific glyphs
fontisan subset font.ttf --glyphs "A,B,C,a,b,c,zero,one,two" --output subset.ttf

From File

# Read characters from file
echo "Hello World" > chars.txt
fontisan subset font.ttf --chars-file chars.txt --output subset.ttf

Retain Glyph IDs

# Keep original glyph IDs
fontisan subset font.ttf --chars "ABC" --retain-gids --output subset.ttf

With Format Conversion

# Subset and convert to WOFF2
fontisan subset font.ttf --chars "ABC" --output-format woff2 --output subset.woff2

Subsetting Strategies

Profile selection

The --profile option controls which font tables the subset retains. The right choice depends on what the subset is for:

Profile	When to use	Notable tables dropped
pdf (default)	PDF embedding, smallest valid output	GSUB, GPOS
web	Browser/web font, retains color-emoji bitmaps + CFF outlines	nothing that browsers need
minimal	Absolute smallest core that still renders	glyf/loca, CFF/CFF2, GSUB/GPOS
full	Lossless re-export	(none)

# Web subset that keeps color-emoji bitmaps so 😀 renders in color
fontisan subset NotoColorEmoji.ttf \
  --chars "😀😁😂🤣😊" \
  --profile web \
  --output-format woff2 \
  --output emoji.woff2

# PDF embedding — drops color bitmaps for size
fontisan subset NotoColorEmoji.ttf \
  --chars "😀" \
  --profile pdf \
  --output emoji-pdf.ttf

Web profile and CBDT/CBLC

The web profile is the only built-in profile that retains CBDT (Color Bitmap Data) and CBLC (Color Bitmap Location) tables. The subsetter walks CBLC to find each retained glyph's bitmap block, rewrites CBDT to keep only those blocks, and rebuilds CBLC's IndexSubTableArray to point at the new offsets. Glyph IDs are remapped through the subset's GlyphMapping, so the output CBLC references subset GIDs, not source GIDs.

Web Font Optimization

# Subset to page content
fontisan subset font.ttf --chars "$(cat content.html)" --output web-font.woff2

Latin Only

# Standard Latin subset
fontisan subset font.ttf --unicodes "U+0000-024F,U+1E00-1EFF" --output latin.woff2

Character Set Presets

# ASCII
fontisan subset font.ttf --unicodes "U+0000-007F" --output ascii.ttf

# Basic Multilingual Plane (BMP)
fontisan subset font.ttf --unicodes "U+0000-FFFF" --output bmp.ttf

Notes

• Subsetting removes unused glyphs and tables
• CFF fonts may require special handling
• Variable fonts are subset while preserving variation
• OpenType features are preserved for included glyphs