| 1. | .in | Input |
| 2. | .in$ | Installation file (HP NewWave) |
| 3. | .in3 | Input device driver (Harvard Graphics 3.0) |
| 4. | .inb | Test script (Vermont HighTest) |
| 5. | .inc | Include file (several programming languages) ◊ Include file subcircuit (Spice) |
| 6. | .ind | Database Index (dBASE IV) |
| 7. | .inf | Hypertext help system file (OS/2) ◊ Information (ascii file) ◊ Setup information, install script |
| 8. | .info | GNU info reader (output from texinfo) (unix) ◊ Icon Data (Amiga) |
| 9. | .ingr | Intergraph Raster File Format |
| 10. | .ini | Bank setup file (Gravis UltraSound) ◊ Initialization file |