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What is a .opf file?
A .opf file is an Obsidium Project File. This one is a specialist format without an obvious everyday home. Confusingly, this extension has been used by 2 different formats over the years — they're all listed below.
This extension has been used by more than one format
2 different formats have claimed .opf over the years, so two files with the same extension aren't necessarily the same kind of thing.
How to open a .opf file
- The program that created it is by far the most reliable way to open it.
- On Windows, use a hex viewer or the free TrID tool to identify what the file really is.
- On Mac or Linux, running `file yourfile` in the terminal identifies most formats instantly.
The registry records this extension against Obsidium Project File, Open Packaging Format, so software from that family is the most likely match.
How to convert a .opf file
- Identify the file first, then look for an export or Save As option in whatever program can read it.
The technical record
For archivists, developers and the merely curious: these are the PRONOM registry entries for .opf.
| Format name | Version | MIME type | PUID |
|---|---|---|---|
| Obsidium Project File | — | — | fmt/207 |
| Open Packaging Format | 3 | — | fmt/2032 |