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Monocle is a modular document reader, with support for different file formats via different backends.

Monocle integrates with the rest of LeechCraft, so, for example, when you click a link to a PDF document in Poshuku, it is suggested to be opened by Monocle after it's downloaded.


  • Tables of contents.
  • Support for links in documents (like in PDF files).
  • Support for forms in documents (like, again, in PDF documents).
  • Displaying annotations in documents like PDF.
  • Support for searching in documents like PDF and FB2.
  • Thumbnails for documents visually highlighting the currently displayed part of the pages.
  • Support for selecting areas and copying them as image or as text (if applicable), or even integrating with the data filters like image uploaders or text searchers.
  • Fullscreen presentation mode.
  • Limited cache for already-rendered images.
  • Displaying one or two pages at once.
  • Paginated navigation.
  • Automatic document reload on document file changes.
  • Integration with the rest of LeechCraft.

The exact feature set depends on the backend used and document type.


Searching in a PDF documentSearching in a PDF document

Data filtersData filters

Page thumbnailsPage thumbnails

PDF document with formsPDF document with forms

DjVu documentDjVu document


Different file formats are supported by different backends. For now the following backends exist:

PDF (Poppler-based)

The most feature-rich backend, based on the Poppler rendering library. It also supports multithreaded threaded rendering on Poppler 0.24.0 and newer, resulting in seamless smooth scrolling and optimal multicore usage if multiple pages are displayed at once.


Self-written parser for fb2 books. Doesn't support images in fb2 documents for now.


Based on the DjVuLibre suite.


Based on the libspectre library.


Based on own implementation.

PDF (mupdf-based)

Another backend for PDF documents. Some claim that it renders more nicely than Poppler. Though, for now it doesn't support links, forms, text searching and possibly some other fancy things Poppler supports.

Please note that since mupdf is built as static library, you need to build mupdf with the -fPIC option.