Free Font Subsetter — Reduce Font File Size for Faster Web Pages

Custom web fonts are one of the biggest hidden performance killers on the internet. A single font file can be 200-400KB. Load four weights (regular, bold, italic, bold italic) and you are adding over a megabyte to every page load — more than some entire websites should weigh. The fix is font subsetting: removing characters you will never use and keeping only what your site actually needs.

Our free font subsetter strips unused characters from any font file. Select predefined character ranges or specify exact Unicode points, then download a dramatically smaller file. A 300KB font becomes 30-50KB. No command line needed, no signup, everything runs in your browser.

Why Font Subsetting Matters for Web Performance

Most fonts ship with thousands of characters covering dozens of languages. A comprehensive font might include Latin, Cyrillic, Greek, Vietnamese, Arabic, Hebrew, and CJK characters — thousands of glyphs. If your website is in English, you are forcing every visitor to download character data they will never see.

The performance impact is real and measurable:

• Download time: A 300KB font on a fast 4G connection takes about 150ms. On a slower 3G connection (common in developing markets and rural areas), that jumps to over 2 seconds. Multiply by the number of font weights you load.
• Render blocking: Browsers typically wait for font files before rendering text. Until the font loads, users either see invisible text (FOIT — Flash of Invisible Text) or a fallback font that suddenly swaps (FOUT — Flash of Unstyled Text).
• Mobile data costs: In markets with metered data plans, every kilobyte costs real money. Sending 1MB of unused font data to mobile users in developing markets is wasteful.
• Caching limits: Mobile browsers have smaller caches. Large font files are more likely to be evicted and re-downloaded on subsequent visits.

Choosing the Right Character Ranges

The key decision in subsetting is which characters to keep. Here are the most common subsets:

Basic Latin (U+0020-007F): 95 characters covering the English alphabet, numbers, and common punctuation. This is the absolute minimum for an English-only site. File size reduction: typically 70-90%.

Latin-1 Supplement (U+00A0-00FF): Add 96 more characters for Western European languages — accented letters for French (e, a, c), German (u, o, a, ss), Spanish (n, a), and more. Essential if your content might include European names, loan words, or international content.

Latin Extended-A (U+0100-017F): 128 characters for Central and Eastern European languages — Polish, Czech, Hungarian, Croatian, and others. Include this for broader European coverage.

Common symbols: Do not forget to include specific characters your site uses: em dash (U+2014), en dash (U+2013), curly quotes (U+201C-201D, U+2018-2019), copyright (U+00A9), trademark (U+2122), bullet (U+2022), and ellipsis (U+2026). Missing any of these causes visible fallback font swaps.

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Before and After — Real Size Comparisons

Here are typical file size reductions from subsetting popular web fonts:

Font	Full Size	Latin Subset	Reduction
Inter Regular	310KB (TTF)	38KB (WOFF2)	88%
Roboto Regular	168KB (TTF)	24KB (WOFF2)	86%
Open Sans Regular	217KB (TTF)	28KB (WOFF2)	87%
Noto Sans Regular	556KB (TTF)	32KB (WOFF2)	94%
Source Sans Pro	288KB (TTF)	26KB (WOFF2)	91%

The combination of subsetting (removing unused characters) and WOFF2 compression (better encoding) produces dramatic results. A font that was 310KB as a full TTF becomes 38KB as a subsetted WOFF2 — small enough that it barely impacts page load even on slow connections.

Impact on Core Web Vitals

Google's Core Web Vitals directly measure the user experience impact of font loading:

• Largest Contentful Paint (LCP): If your largest element is a text block using a custom font, LCP cannot complete until the font loads. A 300KB font on a slow connection can push LCP well past the 2.5-second "good" threshold. Subsetting to 30KB keeps it under budget.
• Cumulative Layout Shift (CLS): When a fallback font renders first and then swaps to the custom font, the text reflows — changing line breaks, spacing, and element positions. This layout shift counts against your CLS score. Faster font loading (from smaller files) reduces the visibility of this swap.
• Interaction to Next Paint (INP): Font files tie up network bandwidth and parsing time. On resource-constrained mobile devices, processing large font files can delay other resources and interactions.

For sites that load multiple font weights, subsetting each weight individually and using the CSS unicode-range property to load only the needed subset for each page can reduce total font payload by 80-95% compared to loading full font files.

Frequently Asked Questions

How much can font subsetting reduce file size?

Subsetting typically reduces font file size by 50-90%, depending on how many characters you remove. A full Unicode font at 300KB might drop to 30-50KB when subsetted to Latin characters only. For fonts with extensive CJK (Chinese, Japanese, Korean) character sets, the reduction can be even more dramatic — from several megabytes down to under 100KB. The exact savings depend on the original font's character coverage and how narrow your subset is.

What characters should I include in a Latin subset?

A standard Latin subset for English-only websites includes: Basic Latin (U+0020-007F) covering letters, numbers, and common punctuation. For Western European language support, add Latin-1 Supplement (U+00A0-00FF) which covers accented characters for French, German, Spanish, and Portuguese. For broader European coverage, include Latin Extended-A (U+0100-017F). Always include common symbols like the em dash, curly quotes, and copyright symbol.

Does font subsetting affect Core Web Vitals?

Yes, positively. Font files are render-blocking resources — the browser waits for them before displaying text. Smaller font files download faster, which directly improves Largest Contentful Paint (LCP) and reduces Cumulative Layout Shift (CLS) from font swap flashes. A 300KB font file on a 3G connection takes over 2 seconds to download. A 40KB subset of the same font downloads in under 300ms. This improvement is especially significant on mobile devices with slower connections.