NSI File

What are NSI files and how to open them

Are you having problems opening a NSI file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your NSI files.

What is a NSI file?

NSI files have multiple uses, and Nullsoft Scriptable Install System (NSIS) Script is one of them. Read more about the other uses further down the page.

Nullsoft Scriptable Install System (NSIS) Script

We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

How to open NSI files

Important: Different programs may use files with the NSI file extension for different purposes, so unless you are sure which format your NSI file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested four different NSI openers which you will find listed below.

Last updated: August 10, 2026

All known file formats using extension .NSI

While Nullsoft Scriptable Install System (NSIS) Script is a popular type of NSI-file, we know of 2 different uses of the .NSI file extension. Different software may use files with the same extension for different types of data.

NorthStar Disk Image (NS DOS)

NorthStar Disk Image (NS DOS) format is a raw disk-image used for North Star Computers floppy disks under their proprietary operating system NSDOS. These files store an exact sector-by-sector copy of a disk's contents, including boot sectors, directory structures, and operating system files. They are primarily used with emulators of the North Star Horizon and related systems to boot or run software exactly as it was stored on the original floppy disk.

These images are written by tools that read physical North Star floppy disks or build disk contents from NSDOS or CP/M filesets, then save them in the .NSI format. Users then mount these .NSI images in an emulator such as NSE (North Star Horizon Emulator), treating them like real floppy disks. Typical operations include listing directory contents, copying files out of the image, or booting the emulator from the image. Some NSI images are created for different disk densities and drive types (single vs double sided, single vs double density) depending on the version of NSDOS.

Internally the .NSI file holds a full raw dump of each track and sector in order: side by side, track by track, and sector by sector. Its size depends on drive parameters (number of tracks, sides, sectors per track, bytes per sector) and density (FM vs MFM). The file begins with a signature that includes the ASCII string "DOS" padded out, followed by identifiable strings such as "COPYRIGHT NORTH STAR COMPUTERS", "PRESS RETURN TO CONTINUE", "COMMAND", and "DISK".

NSI opener for Windows

We have identified one NSI opener that is compatible with this specific type of NSI file.

Various apps that use files with this extension

These apps are known to open certain types of NSI files. Remember, different programs may use NSI files for different purposes, so you may need to try out a few of them to be able to open your specific file.

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about NSI file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.