Libiry

Supported file formats

Libiry supports a wide range of ebook and document formats.

Ebook formats

EPUB (.epub)

The most common ebook format, fully supported.

FeatureSupport
Read metadata✓ Full support
Extract cover✓ Full support
Write tags✓ Full support

Tags are stored in the EPUB’s OPF metadata using <dc:subject> elements.

MOBI/AZW/AZW3 (.mobi, .azw, .azw3)

These are all Amazon Kindle formats.

FeatureSupport
Read metadata✓ Full support
Extract cover✓ Full support
Write tags✓ Via OPF sidecar

Tags are stored in an OPF sidecar file (e.g., book.opf for book.mobi) because these formats don’t support direct metadata editing.

PDF (.pdf)

Portable Document Format.

FeatureSupport
Read metadata✓ Full support
Extract cover✓ First page thumbnail
Write tags✓ In keywords field or OPF sidecar

Some PDFs with encryption or complex structures use OPF sidecar files for tag storage. Use the PDF Tag Checker utility to identify these.

Comic formats

CBZ (.cbz)

Comic book archive (ZIP-based).

FeatureSupport
Read metadata✓ From ComicInfo.xml
Extract cover✓ First image
Write tags✓ In ComicInfo.xml

Metadata is stored in ComicInfo.xml inside the archive.

CBR (.cbr)

Comic book archive (RAR-based).

FeatureSupport
Read metadata✓ Basic support
Extract cover✓ First image
Write tags✓ Via OPF sidecar

RAR archives are read-only, so tags are stored in OPF sidecar files.

Document format

Markdown (.md)

Full markdown support with two metadata formats.

FeatureSupport
Read metadata✓ YAML or flat format
Extract cover✓ From cover field
Write tags✓ Full support

YAML Frontmatter (Obsidian-compatible)

---
cover: "cover.jpg"
booktitle: "The Book Title"
author: "Author Name"
isbn: "978-1234567890"
tags: [fiction, fantasy]
rating: 8
---
 
Book content here...

OPF sidecar files

For formats that don’t support direct tag editing, Libiry uses OPF (Open Packaging Format) sidecar (buddy) files. This includes:

  • MOBI/AZW/AZW3 - Always uses OPF sidecar
  • CBR - Always uses OPF buddy (RAR is read-only)
  • Problematic PDFs - Uses OPF sidecar when direct editing fails
  • All other formats - RTF, MP3, TXT, DOC, etc. automatically use OPF sidecar

How it works

  1. When you edit tags on book.mobi, Libiry creates a book.mobi.opf file
  2. The OPF file stores the metadata in XML format
  3. On reading, Libiry checks for an OPF sidecar file first, then checks the document’s embedded metadata

OPF structure

<?xml version="1.0" encoding="UTF-8"?>
<package xmlns="http://www.idpf.org/2007/opf" version="3.0">
  <metadata xmlns:dc="http://purl.org/dc/elements/1.1/">
    <dc:subject>fiction</dc:subject>
    <dc:subject>fantasy</dc:subject>
    <dc:subject>adventure</dc:subject>
  </metadata>
</package>

Other file formats

Any file type can be added to your library. For formats not listed above (such as .rtf, .mp3, .txt, .docx, etc.), Libiry automatically uses OPF sidecar files for tag storage.

FeatureSupport
Display in grid✓ Shows filename
Read metadataFilename only
Write tags✓ Via OPF buddy file

Simply add the file extension to selected types.txt and Libiry will handle it.

Note: .opf files themselves are not displayed as books.

File type filtering

Configure which file types are displayed in selected types.txt:

.epub
.mobi
.azw
.azw3
.pdf
.cbr
.cbz
.md
.rtf
.mp3

To add a new type, add its extension on a new line.

Format detection

Libiry detects file formats by extension, not by content inspection. Ensure your files have correct extensions.

Cover extraction priority

  1. Embedded cover in ebook metadata
  2. First image for comics (CBR/CBZ)
  3. First page thumbnail for PDFs
  4. Cover field in markdown files
  5. Online lookup from Open Library, Google Books, Europeana

Performance notes

  • Large PDFs may take longer to extract covers
  • Comics with many images are processed efficiently (only the first image)
  • Cache files speed up repeated access

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