| ipynp | IPython Plot Document |
| irb | Interactive Ruby Script |
| irev | LiveCode RevServer Script |
| irobo | RoboMind Source Code |
| is | Modula-3 Intermediate Assembly File |
| is1 | Synergy/DE Data Index |
| isd | InstallShield Dialog |
| isl | InstallShield Pro Log |
| ism | Synergy/DE Data Index |
| isn | InstallShield Skin |
| iss | InstallShield Response File |
| itb | U-Boot uImage Image Tree Blob |
| itcl | Cygwin iwidgets Script |
| itf | JPI TopSpeed Pascal Interface File |
| itq | SAIA S-Web ITQ File |
| its | U-Boot uImage Image Tree Source |
| ivu | ImmerVision XML User Interface |
| ivy2 | Apache Ivy 2 Cache |
| iwb | IWBasic Source Code |
| iwdgt | iWeb Widget |
| iws | IntelliJ IDEA Workspace |
| ixx | Modula-3 Linker Information Data |
| izs | 1st Page 2000 Script |
| j | Java Source Code |
| j3o | JMonkey Engine 3D Object |
| jacl | Java Application Control Language Script |
| jadd | JastAdd Imperative Aspect |
| jade | Jade Markup Language Document |
| jak | AHEAD Tool Suite JAK File |
| jal | JAL Source Code |
| jam | Jam STAPL Source Code |
| jardesc | Eclipse JAR Description |
| jasper | JasperReports Compiled JRXML File |
| jav | Java Source Code |
| java | Java Source Code |