Glagolify is a small Firefox extension that turns Russian Cyrillic text on webpages into Glagolitic. Switch it off and the original text comes back—no reload required.

Choose from four letter styles: Round, Angular Sans, Historical Angular, and Missal Angular. Glagolify also handles text added after a page loads while leaving text fields and editors alone.

Install

Glagolify requires Firefox 142 or newer.

Download the latest .xpi from Releases.
Open about:debugging#/runtime/this-firefox in Firefox.
Select Load Temporary Add-on….
Choose the downloaded .xpi file.

Release builds are currently unsigned, so regular Firefox installs them temporarily and removes them when Firefox restarts.

Use

Open a webpage, click the Glagolify toolbar icon, choose a style, and select Enable Glagolitic. Select Restore Cyrillic when you want the original text back.

Glagolify transliterates letters; it does not translate language. Firefox settings pages, browser UI, and other protected pages cannot be changed.