localtools-font-subsetter

Make web fonts small, on your machine: subset TTF/OTF/WOFF/WOFF2 fonts to the characters you actually use (Unicode presets, your own text, or Unicode ranges), keep or drop OpenType features, drop hinting, pin or limit variable-font axes (e.g. wght 400 to 700), and write WOFF2, WOFF or TTF/OTF. Each result shows before/after size and glyph count, a coverage report (which requested characters the font does not have), font metadata (family, style, axes, license, fsType embedding bits, with a warning when they forbid embedding or subsetting), a live preview rendered with the subset font, and a ready-to-paste @font-face rule with the exact unicode-range. Nothing leaves your computer.

Install

The installer unpacks a portable build with its own Python 3.13 (17 MB zip on Windows, 24 to 39 MB on macOS/Linux).

Use

UI: run localtools-font-subsetter (or the Start menu / Applications launcher). It opens http://127.0.0.1:47129. Drop one or more fonts, tick presets (Latin, Latin Ext, Cyrillic, Cyrillic Ext, Greek, Greek Ext, Vietnamese, or Keep all) and/or type sample text, optionally Unicode ranges, layout features and axes, pick a format, press Subset. The preview line is editable. Copy CSS and Download sit on each result.

• Presets use the same ranges Google Fonts serves, so unicode-range splitting works the way the web expects.
• Layout features: default (fontTools' set: kern, liga, calt, mark, mkmk, locl, ...), all, none, an exact list (kern,liga) or edits to the default (+ss01,+tnum,-liga).
• Axes use fontTools instancer syntax: wght=400 pins, wght=400:700 limits, wght=300:400:700 limits and moves the default, opsz=drop pins to the default. Pin every axis to get a static font.
• Hinting is dropped by default (smaller files; browsers on modern systems barely use it). Tick Keep hinting to keep it.

CLI:

localtools-font-subsetter subset Inter.ttf --preset latin --text "Ωμέγα" --format woff2 -o out/
localtools-font-subsetter subset RobotoFlex.ttf --preset latin,latin-ext --axes "wght=400:700 opsz=drop" -o out/ --css > fonts.css
localtools-font-subsetter subset *.otf --text-file page.html --features +tnum --format woff -o out/ --json

Output files are <name>-subset.<ext>. Missing characters and license warnings go to stderr; --css prints the @font-face rules, --json the full report.

API: POST /api/subset, multipart: file (repeat for several fonts), preset (comma list), text, unicodes, features, hinting (1), axes, format (woff2 woff ttf otf). One font returns the font file, several return a zip with fonts.css. POST /api/report takes the same fields and returns JSON (sizes, glyphs, axes, metadata, coverage, warnings, CSS, base64 font). Errors: 400 {"error": "..."}.

curl -F file=@Inter.ttf -F preset=latin -F text=Hello -F format=woff2 -o Inter-subset.woff2 http://127.0.0.1:47129/api/subset

Engine

fontTools (MIT): fontTools.subset is pyftsubset, and fontTools.varLib.instancer is the reference variable-font instancer; Google Fonts and most font foundries build with them. WOFF2 uses Google's brotli (MIT). The font is subset first and instanced second: that is faster, and it avoids a fontTools failure when subsetting an already partially-instanced font in memory. The full name table (copyright, license, instance names) is kept.

Not included

• Font collections (.ttc/.otc): refused with a clear error; extract a single font first.
• EOT and SVG fonts: obsolete web formats.
• Instancing large variable fonts is slow (a 2 MB, 4,500-glyph font takes about 20 s). Subsetting first helps a lot.

Update / uninstall

localtools-font-subsetter update / localtools-font-subsetter uninstall (installer builds). For PyPI installs: pipx upgrade localtools-font-subsetter / pipx uninstall localtools-font-subsetter.

License

MIT. Test fonts in samples/ are subsets of Inter, Roboto Flex and Noto Sans (SIL OFL 1.1, see samples/licenses/).