Kontakt libraries use .nki files for individual instruments and .nkx files for complete library packages
When you work with Native Instruments Kontakt, you will encounter two main file types. The .nki file is a single instrument — it contains one sound, all its settings, and the samples it uses. The .nkx file is a complete library package that bundles multiple instruments together, often with documentation and presets organized in folders.
Most of the time, you will open .nki files directly in Kontakt. When you download a third-party library from a company like Spitfire Audio or Output, it usually comes as an .nkx file that you install once, and then Kontakt shows you the instruments inside without needing to open individual files each time.
Understanding which file type you are looking at matters because it changes how you load the sound and where Kontakt stores it on your computer. A single .nki file is portable — you can move it between folders and it still works. An .nkx library needs to stay in Kontakt's library folder or it will not appear in your browser.
Key Takeaways
- .nki files are individual instruments that you open directly in Kontakt, and they work the same way whether they are on your desktop or in a library folder.
- .nkx files are packaged libraries that install into Kontakt's system so the instruments appear in your browser automatically.
- When you save your own sound in Kontakt, it saves as .nki by default unless you choose a different format.
- Third-party libraries usually come as .nkx files, but some older or simpler libraries ship as folders of .nki files instead.
The difference between .nki and .nkx files
A .nki file is what Kontakt creates when you design a sound and hit save. It is a single file that contains the instrument itself — the samples, the effects, the mappings, everything needed to play that one sound. You can email a .nki file to someone else, drop it on a USB drive, or store it anywhere on your computer. When you open it in Kontakt, it loads immediately.
A .nkx file is a container. It holds multiple .nki instruments, usually organized by category, plus metadata that tells Kontakt how to display them in the browser. When you install an .nkx library, Kontakt unpacks it into a specific folder on your hard drive — usually something like Documents/Native Instruments/Kontakt 7/Libraries. After that, you never interact with the .nkx file again. You just see the instruments listed in Kontakt's browser.
The practical difference is this: if you want to share a single sound with a collaborator, you send them a .nki file. If you are a company releasing a product with fifty instruments, you package them as .nkx so your customers can install everything at once and it all appears organized in their Kontakt browser.
How to identify which file type you have
Look at the file extension — the letters after the dot at the end of the filename. If it says filename.nki, you have an individual instrument. If it says filename.nkx, you have a library package.
On Windows, file extensions are sometimes hidden by default. To see them, open File Explorer, click the View tab at the top, and check the box next to "File name extensions." On Mac, open Finder, go to Preferences, click the Advanced tab, and check "Show all filename extensions."
If you see a folder instead of a single file, and that folder contains multiple .nki files inside, you have an older-style library. These work fine — you just open the individual .nki files from inside the folder rather than installing a package.
Where Kontakt stores these files on your computer
Individual .nki files can live anywhere. Many people keep them in a dedicated folder on their desktop or in their Documents folder. Kontakt will find them no matter where they are, as long as you navigate to that location when you open the file.
Installed .nkx libraries go into Kontakt's library directory. On Windows, this is usually C:\Users\[Your Username]\Documents\Native Instruments\Kontakt 7\Libraries. On Mac, it is /Users/[Your Username]/Documents/Native Instruments/Kontakt 7/Libraries. The exact path depends on which version of Kontakt you have — Kontakt 6 uses a Kontakt 6 folder, Kontakt 7 uses Kontakt 7, and so on.
When you install an .nkx file, Kontakt automatically unpacks it into the correct library folder. You do not have to move files manually. If you ever want to uninstall a library, you delete the folder that Kontakt created for it in the Libraries directory.
Other file types you might see in Kontakt
Beyond .nki and .nkx, Kontakt works with a few other formats. .nkm files are multis — they are collections of .nki instruments stacked together so you can play multiple sounds at once from different keyboard zones. You open a .nkm file the same way you open a .nki file.
.nks files are snapshots of a single instrument's settings at a moment in time. They are much smaller than .nki files because they only store the parameter values, not the samples themselves. If you load a .nks file, Kontakt applies those settings to whatever instrument is currently loaded.
You will also see .wav, .aif, and .flac files inside library folders. These are the actual audio samples that Kontakt plays. You do not open these directly — Kontakt reads them automatically when you load an instrument that uses them.
How to open and save these files
To open a .nki or .nkm file, launch Kontakt and go to File > Open. Navigate to wherever the file is stored and double-click it. The instrument loads into the Kontakt window and you can play it immediately.
To save your own instrument as a .nki file, design your sound in Kontakt, then go to File > Save Instrument. Choose a location on your computer and give it a name. Kontakt saves it as .nki by default. If you want to save it as a .nks snapshot instead (just the settings, not the samples), go to File > Save Snapshot.
You cannot create .nkx files yourself unless you are using Kontakt's advanced library tools, which are built into Kontakt but require some setup. Most people never need to do this. If you are just sharing sounds with friends or colleagues, stick with .nki files.
Troubleshooting when files do not load
If you try to open a .nki file and Kontakt says it cannot find it, the most common reason is that the file is missing its samples. A .nki file contains references to where the samples are stored, but if you moved the samples folder without updating the references, Kontakt cannot locate them. The solution is to use Kontakt's File > Manage Library > Rescan Library function, which tells Kontakt to search for missing samples.
If an installed .nkx library is not showing up in your browser, try restarting Kontakt. Sometimes the browser does not refresh immediately after installation. If it still does not appear, go to Kontakt's preferences and check that the library folder path is correct.
If you are trying to open a .nki file and get an error about the file being corrupted, the file may have been damaged during download or transfer. Try downloading it again or asking the person who sent it to you to resend it.
Frequently Asked Questions
Can I convert a .nki file to .nkx or vice versa?
Not directly. A .nki is a single instrument and a .nkx is a packaged library — they serve different purposes. If you want to bundle multiple .nki files into a library, you would need to use Kontakt's library creation tools, which is a more advanced process. For most users, it is simpler to just keep .nki files in a folder and open them individually.
What happens if I delete a .nkx file after installing it?
Nothing bad happens. Once Kontakt unpacks a .nkx file, the library is stored in your Kontakt library folder. The original .nkx file is no longer needed. You can delete it to save disk space. The instruments will still appear in Kontakt's browser.
Can I move a .nki file to a different folder without breaking it?
Yes, as long as the samples it uses move with it. If you have a .nki file that uses samples stored in a separate folder, move both the .nki and the samples folder together. If you move only the .nki file, Kontakt will not be able to find the samples when you try to load it.
Do I need to install .nki files, or can I just open them?
You can just open them. .nki files do not need installation — you navigate to wherever they are stored and open them directly in Kontakt. Installation is only for .nkx libraries, which Kontakt unpacks automatically.
Why does my third-party library come as a .nkx file instead of individual .nki files?
Packaging as .nkx makes installation easier for customers and keeps the library organized. Instead of downloading fifty separate files, you download one .nkx file, Kontakt installs it, and all the instruments appear organized in your browser. It is a convenience feature for larger libraries.