NSF File

What are NSF files and how to open them

Are you having problems opening a NSF 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 NSF files.

What is a NSF file?

NSF files have multiple uses, and NES Sound Format Audio is one of them. Read more about the other uses further down the page.

NES Sound Format Audio File

These NSF files are audio files that contain music and sound effects from Nintendo Entertainment System (NES) video games. The NES was a popular home video game console released in the 1980s, and NSF files are used to store and play back the audio, often both music and sound effects, from NES games.

How to open NSF files

We have identified three NSF openers that are compatible with this specific type of NSF file.

Programs that open NES Sound Format Audio files

Last updated: August 4, 2026

All known file formats using extension .NSF

While NES Sound Format Audio File is a popular type of NSF-file, we know of 3 different uses of the .NSF file extension. Different software may use files with the same extension for different types of data.

Lotus Notes Database

A Lotus Notes Database file, using the .NSF extension, is a single binary database used by IBM Lotus Notes (now HCL Notes) and the Domino server to store emails, calendar entries, contacts, applications, views, forms, folders, design elements, and other items ("notes") in one file. It allows for offline work via a local replica of the database, with later synchronization (replication) to keep server-based copies updated.

The application that creates .NSF files is IBM Lotus Notes / HCL Notes when a user or administrator sets up a database. Templates (.NTF files) define design elements; once a database is created it is saved as .NSF. Within Notes or Domino, users work with "notes" (both data notes like email or documents and design notes like forms and views), access control via ACL, and optional encryption tied to a user's identity file.

Technically the NSF file begins with a binary header including signature bytes; the format is non-relational/document-oriented. Internal structure includes a file header followed by a database header containing identifiers, versioning, replication history, and then blocks for data such as summaries, non-summary buckets, bitmaps, and other record relocation vectors. According to common magic bytes, the first few bytes are 1A 00 00 04 00 00.

NSF opener for Windows

We have identified 2 NSF openers that are compatible with this specific type of NSF file.

NATO Secondary Imagery Format

We know that one NSF format is NATO Secondary Imagery Format. We have not yet analyzed in detail what these files contain and what they are used for. We're working on it.

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

Various apps that use files with this extension

These apps are known to open certain types of NSF files. Remember, different programs may use NSF 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 NSF file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.