| idl | Interface Definition File |
| idle | IDle Script Source |
| idll | CodeWarrior DLL |
| idml | Adobe InDesign Markup Language Document |
| idn | Alpha Five Index Definition File |
| idol | IDle Object Library |
| idt | Windows Installer Exported Database |
| idy | Micro Focus COBOL Debug Data |
| iex | Elixir Interactive Shell Script |
| ifm | IBM WebSphere Interface Mapping |
| ifm | FactoryTalk View Studio Information Message Component File |
| ifr | UEFI IFR Opcode |
| ih | C++ Internal Header |
| ihex | Intel HEX Format Data |
| ihp | Watcom C Compiler Help |
| ihx | Intel HEX Format Data |
| ijl | J Locked Script |
| ijr | J Runtime Script |
| ijs | J Script File |
| il | IL Source Code |
| il | Cadence SKILL File |
| 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 | Micro Focus COBOL Intermediate Code |
| int | Delphi Interface Unit |
| iobj | Visual Studio Intermediate Object |
| iot | Hitachi Ladder Editor IO Comment |
