A small, fast, responsive font tester that runs entirely in the browser. Drop one or more font files on the page, type or pick a specimen text, and play with size, line height, variable axes and OpenType features. Built for type designers, with Arabic(mostly focused on Farsi) / Latin scripts in mind.

No build step, no dependencies, no server, no tracking: three static files (index.html, script.js, style.css).

A large part of this project was designed and written in collaboration with Claude (Anthropic's AI assistant).

• Load fonts your way: drag & drop (several files at once), the + Font button, or a URL. Supports ttf, otf, woff and woff2.
• Several fonts at the same time: every font is a chip you can select, reload (↻) or remove (×). Each font remembers its own variable-axis and OpenType settings.
• Auto-reload: when a font file changes on disk (for example, after you export it from your font editor), it reloads by itself. Toggle it with the round ↻ button next to the dark-mode button.
• Variable fonts: axes are read from the font's fvar table and turned into sliders. A 🎲 button randomizes them.
• OpenType features: the feature list is read from the font's GSUB / GPOS tables. All +N also shows the shaping features hidden by default (init, medi, fina, ccmp, locl…). You can add your own 4-letter tag with a default value (1, 0, on, off).
• Layout controls: size, line height, outline mode, text alignment (right / left / justify) and Guides, which draw the ascender, descender (solid lines), x-height and cap-height (dotted lines) under every line of text.
• Specimen texts: built-in tests for Persian, Arabic, Quran, English, numbers, ZWNJ, Arabic marks, kerning pairs and full layout pages. Add your own with +, remove any of them with ×.
• Wikipedia mode: the Wiki button in the Test tab fetches a long random article in Persian, Arabic, English or any language code you type.
• About popup: the i button(on top-right corner) shows the notes, author and link of the current test, or the link of the Wikipedia article.
• Copy CSS: click the small CSS line in the Layout, Variation and OpenType tabs to copy font-size, font-variation-settings or font-feature-settings.
• Dark mode, RTL/LTR text, and a layout that works on phones (the bottom bar scrolls horizontally, no scrollbars).

1. Download or clone the repository.
2. Open index.html in a browser.

Opening the file directly works. Serving it over HTTP is recommended (auto-reload of fonts loaded by URL needs it). The simplest way:

python3 -m http.server
# then open http://localhost:8000

It also works on GitHub Pages or any static host.

The bar at the bottom has six tabs (on a mouse device, hovering a tab title opens it):

Tip: the text on the page is editable. Type, paste or edit it directly.

⬇ exports fft-backup.json; 📂 (or dropping the .json file on the page) imports it. Tests and custom features are added to your list (duplicates are skipped); settings are replaced.

{
  "app": "FFT",
  "version": 1,
  "settings": { "dark": true, "autoReload": true, "wikiLang": "fa" },
  "tests": [
    { "name": "My test", "text": "…", "about": "…", "author": "…", "link": "https://…" }
  ],
  "features": [ { "tag": "ss05", "on": true } ]
}

Only plain-text tests are exported (the built-in layout pages are code, not data). Links must start with http:// or https://.

At the end of the Test row, in a red dashed box: ↺ adds back built-in tests that you deleted, 🗑 deletes everything FFT saved in this browser (tests, theme, Wikipedia language, custom features) and reloads the page.

Everything stays in your browser. Tests, custom OpenType features, theme, auto-reload and Wikipedia-language settings are kept in localStorage (keys starting with fft-). Fonts are never saved; refreshing the page clears them. The only network requests are the ones you ask for: Wikipedia (when you press Fetch article) and fonts you load by URL.

• Chrome / Edge (desktop) give the full experience. Auto-reload of local files uses the File System Access API: fonts added with + Font or by drag & drop are watched for changes. Firefox and Safari can't watch local files, so use the ↻ button on the chip.
• woff2: reading its tables (axes, features, name) needs Brotli support in DecompressionStream. Without it the font still renders, but a generic feature list is shown and variable axes can't be listed. ttf, otf and woff always work.
• Fonts by URL need the server to allow CORS.
• Guides are measured from the Latin glyphs (b d h k l, p q, x, H). For a font without Latin letters, the values in the font's hhea / OS/2 tables are used instead.
• The Fallback font is whatever the browser uses for system-ui; browsers don't tell which font that is, so no axes or feature list can be read for it.

index.html   markup, the footer tabs, inline SVG icons
style.css    all styles (light / dark, responsive)
script.js    everything else: font parser, UI, tests, Wikipedia, backup

• Built-in test texts by Amin Abedi, Saleh Souzanchi, AmirMahdi Moslehi and Pablo Impallari (Impallari Font Testing Project). Each test shows its author in the i popup.
• Some specimen texts, and the articles fetched in Wikipedia mode, come from Wikipedia and remain under their own license, CC BY-SA.
• Made with Claude (Anthropic).

MIT © 2026 Amin Abedi. The MIT license covers the code; the Wikipedia texts keep their own license.