| ijr | J Runtime Script |
| ijs | J Script File |
| il | Cadence SKILL File |
| il | IL Source Code |
| ile | Encrypted Cadence SKILL File |
| ilk | Visual Studio Incremental Link File |
| iml | IntelliJ IDEA Module |
| in7 | Ox Data |
| ina | Alpha Five Form Definition Data |
| inc | ASP Include File |
| inc | General Include File |
| incr | Visual C# Compiler Incremental Data |
| inn | Micro Focus COBOL Overlay File |
| ino | Arduino Sketch |
| int | Delphi Interface Unit |
| int | Micro Focus COBOL Intermediate Code |
| inventor | SGI Open Inventor Data |
| iobj | Visual Studio Intermediate Object |
| iot | Hitachi Ladder Editor IO Comment |
| ipb | Apple iOS Perl Script |
| ipch | Intellisense Precompiled Header |
| ipdb | Visual Studio Internal Compilation Database |
| ipdl | IPC Protocol Definition Language Document |
| ipnb | IPython Notebook Document |
| ipy | IPython Script |
| ipynb | IPython Notebook Document |
| ipynd | IPython Notebook Document |
| ipynp | IPython Plot Document |
| irb | Interactive Ruby Script |
| irev | LiveCode RevServer Script |
