| sym | VariCAD Symbol Library |
| symbols | Debian Package Extended Shared Library Information Data |
| syn | TextPad Syntax File |
| sync | Apple ColorSync Data |
| syncdb | iTunes Sync Database |
| syncml | Open Mobile Alliance SyncML Data |
| syr | Xilinx XST Synthesis Report |
| sys | Microsoft SQL Server Data Replication System Table Data |
| sys | General Swap File |
| syx | MIDI System Exclusive Message |
| syz | SYSTAT Data |
| sy_ | Compressed SYS File |
| sz | WinAMP Skin |
| sz4 | E-triloquist Phrase Library |
| szs | Wii Game Data |
| szx | Spectaculator ZX-State Snapshot |
| t$m | AVG Internet Security Temporary File |
| t00 | TaxCut Federal Data |
| t01 | TaxCut Federal Data |
| t02 | TaxCut Federal Data |
| t03 | TaxCut Federal Data |
| t04 | TaxCut Federal Data |
| t05 | TaxCut Federal Data |
| t06 | TaxCut Federal Data |
| t07 | TaxCut Federal Data |
| t08 | TaxCut Federal Data |
| t09 | TaxCut Federal Data |
| t10 | IRIG 106 Data Transfer Data |
| t12 | At Home 2012 Tax Return Data |
| t13 | At Home 2013 Tax Return Data |
| t15 | H&R Block 2015 Tax Return Data |
| t16 | H&R Block 2016 Tax Return Data |
| t2flow | Taverna v2 Workbench Workflow Definition |
| t2g | Kallisto Transcript to Gene Data |
| t2k | Teach2000 Document |