| ldata | JSim Line Data Format |
| ldb | Microsoft Access Database Lock |
| ldb | Sybase PowerDesigner Logical Data Model Backup |
| ldc | Steuer 2001 Data File |
| ldd | Laser Dispatch Data File |
| lde | Veeam Explorer Exported Data |
| ldf | LogPlot LogDesign File |
| ldf | Lingoes Dictionary Source |
| ldf | LDAP Data Interchange Format File |
| ldf | Microsoft SQL Server Transaction Log |
| ldfx | LogPlot LogDesign XML File |
| ldg | TIBCO Business Studio Ledger Data |
| ldi | LDAP Data Interchange Format File |
| ldif | LDAP Data Interchange Format File |
| ldk | Larson Davis System 824 Firmware Authorization Data |
| ldl | Paradox Delivered Library |
| ldm | Sybase PowerDesigner Logical Data Model |
| ldp | Active Directory Exported LDAP Data |
| ldt | Oracle Generic Loader Data File |
| ldt | EULUMDAT File |
| led | AIBO LED File |
| lef | EnCase Logical Evidence Data |
| lef | LEN Exchange Format File |
| len | Esko PlatePrep Len File |
| leo | Leo Editor Outline Data |
| lepf | Little Endian Prebuilt Format File |
| les | Mklesson Lesson File |
| les | TurboWin LES Data |
| lesshst | Less History File |
| lex | Microsoft Office Custom Dictionary |
| lexe | SciTE Data |
| lext | Olympus LEXT Measurement Export Data |
| lfa | Life Forms Studio Motions Data |
| lfb | Laserfiche Briefcase |
| lfe | Laserfiche Shortcut |