[GUI Plugin] OPF Helper

[Comfy.n]

OPF Helper is a toolkit for inspecting, validating, and managing OPF files in your EPUB library. It offers advanced search, export, and troubleshooting 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 validation, 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 (currently limited) 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

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 Finder

EPUB version scanner (3.0, 2.0, or non-3.0)
Supports targeted maintenance and conversion workflows

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

Spoiler:

version 1.0.2
Initial implementation of OPF Standards comparison

version 1.0.1
Debug output now fully suppressed unless explicitly enabled

[Comfy.n]

reserved

[JSWolf]

Why do we have a thread for a non-existent plugin?

[BeckyEbook]

Shhh... It's definitely going to be a surprise.
I understand the situation perfectly. The plugin was almost ready, but just before publication, it turned out that there was a bug that needed to be fixed. Regular forum users cannot delete threads or posts, so let's just wait patiently.

[Comfy.n]

Originally Posted by BeckyEbook

Shhh... It's definitely going to be a surprise.
I understand the situation perfectly. The plugin was almost ready, but just before publication, it turned out that there was a bug that needed to be fixed. Regular forum users cannot delete threads or posts, so let's just wait patiently.

Originally Posted by JSWolf

Why do we have a thread for a non-existent plugin?

hahaha

I think it will take some time for me to make my mind up about the first official release.

I needed the thread URL!

[JSWolf]

Has anyone actually seen an ePub with multiple OPF files? I have not.

How does this differ from using epubcheck to check for OPF errors?

[Comfy.n]

Originally Posted by JSWolf

Has anyone actually seen an ePub with multiple OPF files? I have not.

I've seen a few. Very rare though.

How does this differ from using epubcheck to check for OPF errors?

Hmm, I haven't used epubcheck much. This plugin validation is implemented mostly as a hint and educational feature; it's definitely not intended to be taken as a strict validation tool.

I don't make ebooks BTW. Just once for my niece, actually. So I'd appreciate every feedback to this tool. If it can be improved validation-wise, this wouldn't be something I have enough experience to do.

[Comfy.n]

Here's one example

[milady133]

Hi @comfy.n,
I'm not clear if you can use this plugin when you want to just edit the opf file inside the epub, without editing the rest, or if it's only to check and extract information from this file for the epubs in your calibre library.
I edit all the epubs I load into my Calibre library, but for a lot of them, I only touch the opf file doing some minor fixes: checking that the cover is properly labeled so it shows in the UI of the library program I'm using, checking the ISBN is informed when the publisher is using it, making sure that the series info is present, and some other minor fixes.
Regards

[BetterRed]

@Comfy.n - as I said elsewhere, what I know about OPF files would fit onto the back of a penny black. Never the less I had a play around. I don't understand why "Find non-EPUB 3.0 books" finds books which have neither an EPUB nor a KEPUB.

I've attached an EPUB 2.0 file, what am I expected to make of this:



The epub gets a green tick from the calibre book editor and Sigil - I don't have epubcheck (Java the language it's okay-ish, but on Windows Java run time is not okay - IMO)

---

I see OPF Helper is, like CCR, non-modal. I don't have a problem with that per se.

But, and I've been meaning to ask this in respect to CCR, if the library manager is run full-screen and the CCR and OPF Helper windows are "popped", then one would see something like this:



If I click on calibre main window it will be bought to the front and the CCR and OPF Helper windows will be out of sight. How is the user meant to deal with that - on Windows*, and on MacOS, and on umpteen flavours of Linux.

You might want to have a look at how the calibre book editor handles the Spellchecker and Reports windows, which are also non modal… but they can't get trapped behind the main window. If they're in the way, I press Ctrl+Win+T (stay on top), Ctrl+Win+R (roll up) and park them somewhere.



BR

* on Windows it can be dealt with via the Taskbar, but how exactly depends on Taskbar settings and its current state.

[Comfy.n]

Originally Posted by milady133

Hi @comfy.n,
I'm not clear if you can use this plugin when you want to just edit the opf file inside the epub, without editing the rest, or if it's only to check and extract information from this file for the epubs in your calibre library.
I edit all the epubs I load into my Calibre library, but for a lot of them, I only touch the opf file doing some minor fixes: checking that the cover is properly labeled so it shows in the UI of the library program I'm using, checking the ISBN is informed when the publisher is using it, making sure that the series info is present, and some other minor fixes.
Regards

Hi @milady133! Thank you so much for your inputs. Yes.. it was originally intended just as a quick OPF Viewer/inspector, but I am trying to implement the Edit feature. Going through the Unpack Book path (native calibre function) is possible, but it is not as direct as desirable.

[Comfy.n]

@BR I will take a careful look at each one of your remarks, later.

[Comfy.n]

Originally Posted by milady133

Hi @comfy.n,
I'm not clear if you can use this plugin when you want to just edit the opf file inside the epub, without editing the rest, or if it's only to check and extract information from this file for the epubs in your calibre library.
I edit all the epubs I load into my Calibre library, but for a lot of them, I only touch the opf file doing some minor fixes: checking that the cover is properly labeled so it shows in the UI of the library program I'm using, checking the ISBN is informed when the publisher is using it, making sure that the series info is present, and some other minor fixes.
Regards

Done! Please check out version 1.0.4?