| lcf | ArchiCAD Library Container File |
| lcl | LISCAD Lite Database |
| lcm | Lipikar Custom Map |
| lcn | Trymedia License Data |
| lcp | FARSITE Landscape Data |
| lcpl | Readium License Document |
| lcs | Light-O-Rama Compressed Sequence File |
| lcs | L0phtCrack Password Database |
| lcs | Alstom MMS LCS Compiler Report |
| lcv | Radio Mobile Land Cover Data |
| lcx | LC Model |
| ld | MoTeC Telemetry Log |
| ld1 | dBASE IV Overlay File |
| ld2 | Lingoes Compiled Dictionary |
| ldata | JSim Line Data Format |
| ldb | Sybase PowerDesigner Logical Data Model Backup |
| ldb | Microsoft Access Database Lock |
| ldc | Steuer 2001 Data File |
| ldd | Laser Dispatch Data File |
| lde | Veeam Explorer Exported Data |
| ldf | Microsoft SQL Server Transaction Log |
| ldf | LogPlot LogDesign File |
| ldf | LDAP Data Interchange Format File |
| ldf | Lingoes Dictionary Source |
| 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 | EULUMDAT File |
| ldt | Oracle Generic Loader Data File |
| led | AIBO LED File |