Data file
What is a .nii file?
A .nii file is a The Neuroimaging Informatics Technology Initiative File Format (version 1). This is a data file — structured information used by a program rather than read directly. 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 .nii over the years, so two files with the same extension aren't necessarily the same kind of thing.
How to open a .nii file
- Start with the program that produced it; that's almost always the right tool.
- Open it in a text editor to see whether it's readable text or binary.
- For database formats, DB Browser for SQLite or LibreOffice Base can often import it.
The registry records this extension against The Neuroimaging Informatics Technology Initiative File Format, The Neuroimaging Informatics Technology Initiative File Format, so software from that family is the most likely match.
How to convert a .nii file
- If you can view the data, exporting to .csv is usually the most portable option.
The technical record
For archivists, developers and the merely curious: these are the PRONOM registry entries for .nii.
| Format name | Version | MIME type | PUID |
|---|---|---|---|
| The Neuroimaging Informatics Technology Initiative File Format | 1 | — | fmt/798 |
| The Neuroimaging Informatics Technology Initiative File Format | 2 | — | fmt/1094 |