ZenReaderFx от vidhyarthi

Article extraction — Uses Mozilla Readability to strip ads, navigation, and clutter from any article
Bookmarks panel — Floating draggable outline built from headings (H1-H6), bookmark icons, active section highlight, scroll-to-top chevron
Dark mode — Full dark theme (neutral grays, VS Code Dark+ syntax highlighting). Auto-detects system preference.
Reading progress — Thin gradient bar at the top; hover anywhere on it to see percentage
Syntax highlighting — Code blocks are highlighted with language-specific colored left borders (Python, C++, Rust, JS, etc.)
Math rendering (KaTeX) — LaTeX math from MathJax/KaTeX pages is recovered and typeset as real equations (inline $…$ and display $$…$$), even on async MathJax pages where the source is normally lost
PDF export via print dialog — Choose "Save as PDF" in Firefox's native print dialog; page size/margins carry over from the export dialog
Markdown export — Save the cleaned article as a .md file, preserving headings, code fences (with language), lists, tables, and links
Focus mode — Dims all but the block you're reading for a spotlight effect (Alt+O); remembered across reloads and never dims your print output
Layout density — Compact / Comfortable / Spacious presets adjust line spacing and column width in one click (remembered across reloads)
Custom CSS — Apply your own styles to the reader from the Appearance popover (remembered across reloads)
Reading stats — Estimated read time + word count; live word count for any text you select
Bundled fonts — All 13 font families work offline (latin subset, ~500KB total)
Custom fonts — Adjust body and code font family, size, and weight from the Appearance popover
Movable, groupable toolbar — Drag the toolbar anywhere by its grip handle (position remembered); minimize it into a gear button; buttons grouped View / Edit / Export
Edit tips — Contextual hints shown when edit mode is first activated (Alt+T to toggle manually)
Private browsing support — Works in private windows; history and reading positions are not saved
Edit mode — Toggle pencil icon (or Alt+E) to enable hover-to-delete and double-click-to-edit. Alt+hover also works as a shortcut.
Grouped deletion — Shift+click the delete button to remove all similar elements at once
Undo support — Ctrl+Z to undo deletions, text edits, and image resizes (up to 50 actions)
Image resize — Click any image to select it, then resize to 25%, 50%, 75%, or 100% width. Ctrl+click to select multiple images
Keyboard shortcuts — Alt+? shows full cheatsheet. Alt+ B/D/F/E/O/T/P/S/M for all actions, Esc to close panels
Smart page breaks — Headings stay with their content; code blocks and images don't split across pages
Ligature-free code — Code blocks disable font ligatures to correctly display tokens like <|end_of_text|>
Auto-collapsing UI — Right toolbar and banner fade/collapse after 10s of inactivity, maximizing reading space
Responsive — Bookmarks panel adapts to narrow viewports (<700px becomes overlay)