| nifcache | Gamebryo NIF Cache |
| nii | NIfTI-1 Data Format File |
| nil | Norton Icon Library File |
| nin | BLAST Nucleotide Database |
| niv | theWord New International Version Module |
| nix | IBM Rational XDE Node Instance File |
| nj | MOLPHY Neighbor Joining Phylogeny Data |
| nja | Seifert XRD ASCII Pole Figures Data |
| njb | Nikon Photo Index |
| njc | Seifert XRD Pole Figures Data |
| njf | Lotus Notes Job Data |
| nji | Nero BackItUp Job Information |
| njob | NDARC Job Data |
| njt | Nero BackItUp Job Template |
| nk2 | Microsoft Outlook 2002 Auto Complete Nick List |
| nka | NI Abbey Road Drummer Data |
| nkd | Nikon ViewNX Thumbnail Cache |
| nkfn | Kernel for NTFS Data Recovery Snapshot Data |
| nkg | Native Instruments Kontakt Groups |
| nkjv | theWord New King James Version Module |
| nksc | Nikon Capture NX-D Sidecar Data |
| nksf | Native Kontrol Standard Presets Library |
| nksn | Native Instruments Kontakt Settings |
| nksr | NI REAKTOR Rack Data |
| nkt | nKPRO Telemetry Data |
| nkv | PLDA Shared Model |
| nl | newlook Screen Data |
| nl | AMPL NL Problem File |
| nl2 | eSignal Market Depth Data |
| nlang3 | Ashampoo Internet Accelerator Localisation Data |
| nlb | Oracle Locale Builder Binary File |
| nlc | Nero Linux Compilation |
| nld | Norland Image Format File |
| nlf | ClickTracks Normalized Log File |
| nlf | MicroSim PCBoard Netlist |