OPF File Extension
Have a problem opening a .OPF file? We collect information about file formats and can explain what OPF files are. Additionally we recommend software suitable for opening or converting such files.
What is the .OPF file type?
The .opf filename extension has its primary association with the Open Packaging Format (OPF). OPF an open XML-based packaging and metadata description format for electronic publications (e-books) developed by the International Digital Publishing Forum (IDPF). Along with other two open standards (OCF and OPS), OPF is part of the EPUB format.
An .opf file is typically a small (a couple of kilobytes) text-only XML file that follows some version of the OPF Specification (IDPF). Basically, OPF files contain metadata for e-book titles. There can be editorial reviews, summaries, publisher's details, ISBN indexes, cover references (with cover image files usually placed in the same directory), and so on.
To preserve metadata for a given e-book title, its companion .opf file should remain in the same directory. E-books in the EPUB format store OPF metadata internally, in the "content.opf" file inside the .epub archive (ZIP). OPF files are understood by most e-book reader devices and extensively used by e-book organizers/readers.
Not to be confused with the above Open Packaging Format (OPF), the .opf extension was also associated with the Open eBook Package File (OPF) format. Open eBook (OEB) is a legacy, pre-EPUB open format previously developed under the auspices of IDPF, but later completely abandoned in favor of EPUB. OEB is an XML/HTML-based format, and an .opf file is a text file with XML-structured data inside. It is a source file, providing a list of all files included in the current e-book build and a set of metadata keys.
Alternatively, the .opf extension has another association with the Obsidium Project File (OPF) file type and format. Obsidium is a commercial software protection and licensing management tool for Microsoft Windows by Obsidium Software, designed to safeguard proprietary software from cracking and unauthorized use. Obsidium uses .opf files to stores its projects. An Obsidium project (.opf) stores all settings and preferences for the Obsidium protection engine applied to a given piece of software.
Additionally, the .opf extension also relates to the FlipAlbum Book (.opf) file type/format. FlipAlbum is a free/paid Microsoft Windows software by E-Book Systems that uses realistic page-flipping effects and adds other features to make virtual photo and multimedia albums. FlipAlbum applications use text .opf files, saved in a private XML-based format, to store virtual album books, either with (in a separate subfolder) or without the actual content.
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