Font Styler for LLMs by JG

What's the problem?

If you write Persian in Gemini, Claude, ChatGPT or similar chatbots, you have probably noticed that Persian text doesn't look good. The main fonts of these sites are designed mostly for Latin letters and don't include Persian ones. To show each Persian letter, the browser has to fall back to some font from your operating system. That font differs from one device to another, is often a poor choice for reading long text, and looks out of place next to the English text.

What does this extension do?

It changes the font of Persian (and Arabic) text only, using a font you choose. The default is Vazirmatn. The key point: nothing else is touched. English text, buttons, menus and icons keep the site's own fonts. Even in a mixed sentence, the Persian letters are shown in your chosen font and the English letters in the site's font.

Features

Only Persian text changes; the rest of the site looks exactly as before.
Vazirmatn is built in. No internet connection or outside service (such as Google Fonts) is needed.
From the extension's popup you can pick a font from the available ones and switch the extension on or off.
Add your own font: import a font file (woff2, woff, ttf or otf) from the "Import / manage fonts" page. You can import several files together (for example Regular and Bold) to make one complete font. Imported fonts are stored only inside your browser and can be deleted at any time (limits: 4 MB per file, 8 MB in total).
Changes apply instantly, with no page reload. Text that appears while an answer is being written is shown in the chosen font right away.
Optional "Digits and punctuation" setting: when on, digits and punctuation inside text that contains Persian also use the chosen font, so Persian sentences look more uniform. English-only text stays untouched.
Lightweight: only elements that contain Persian text are changed.

Supported sites

Gemini (gemini.google.com), Claude (claude.ai), ChatGPT (chatgpt.com), DeepSeek (chat.deepseek.com), Qwen (chat.qwen.ai), Kimi (kimi.com), Mistral Le Chat (chat.mistral.ai) and Microsoft Copilot (copilot.microsoft.com).

Privacy

The extension does not collect or send any data and makes no network requests. It only has access to its own settings storage and to the eight sites above. To detect Persian text, it checks the page's text locally in your browser; none of it is stored or sent anywhere.

Good to know

Requires Firefox 140 or newer (Firefox 142 on Android).
Arabic and Urdu use the same script, so Arabic and Urdu text also uses the chosen font.
Depending on the font you choose, the line height of lines containing Persian text may differ slightly from before.
Sites not listed above are not supported.

Credits and licenses

This extension is based on the open-source project Gemini_Vazirmatn_Styler (MIT license, github.com/IAUCourseExp/Gemini_Vazirmatn_Styler). The Vazirmatn font is included under the SIL Open Font License 1.1.