OPF Helper is a toolkit for inspecting, scanning, and managing OPF files inside book formats in your library.
It offers advanced search, export, and basic validation features to help you maintain clean, standards-compliant metadata and structure in your Calibre collection.
The plugin began as a simple OPF viewer, but grew to include version scanners, batch search, and export tools for power users and ebook maintainers. It is the result of a 'learning-by-doing' initiative focused on learning about OPFs.
The plugin provides a streamlined interface with basic keyboard shortcut support and is organized around several core features:
Show OPF Content
Instantly view the OPF file for any selected book(s)
Syntax highlighting and easy copy/export options
Find Multiple OPF Files
Edit OPF
Starting from version 1.0.4, OPF Helper provides an Edit OPF feature, including a button to run calibre's action 'Set metadata from OPF".
Scan your library for books with more than one OPF file
Quickly filter and review multiple OPF books
Find XML Parsing Issues
Detect and report XML errors in OPF files across your library
Helps identify and fix problematic metadata
Export Selected OPFs
Export OPF files from selected books to a chosen folder
Useful for backup, sharing, or external editing
EPUB version scanner (3.0, 2.0, or non-3.0)
Supports targeted maintenance and conversion workflows
Starting from version 2.0, can scan also MOBI and AZW3
Bulk validation
New feature for parallel validation of OPF files inside your books, with scope on library or selected books
Common OPF Warnings
A catalog of common OPF related warnings consistent with schema-based validation, under Resources tab.
Tips
The validation tab is implemented mostly as a hint and educational feature; it's definitely not intended to be taken as a strict validation tool.
Compatibility
Calibre 5.44 or later
Works on Windows, macOS, and Linux (tested on Windows; feedback for other platforms welcome)
License
This plugin is licensed under the GNU GPL v3
Hope you enjoy it!
Release notes