| Extension | File Description |
| .AC$ | Misc Files |
| .AC0 | Uncommon Files |
| .AC1 | Uncommon Files |
| .AC2 | Uncommon Files |
| .AC3 | Audio Files |
| .AC4 | Uncommon Files |
| .AC5 | Uncommon Files |
| .AC6 | Uncommon Files |
| .AC7 | Uncommon Files |
| .AC8 | Uncommon Files |
| .AC9 | Uncommon Files |
| .ACA | Data Files |
| .ACAD | Uncommon Files |
| .ACAS | Uncommon Files |
| .ACB | Settings Files |
| .ACC | Data Files |
| .ACCDB | Database Files |
| .ACCDE | Database Files |
| .ACCDR | Database Files |
| .ACCDT | Database Files |
| .ACCESS | Uncommon Files |
| .ACCESSPRIV | Uncommon Files |
| .ACCOLADE | Uncommon Files |
| .ACCORD | Uncommon Files |
| .ACCT | Uncommon Files |
| .ACD | Developer Files |
| .ACE | Compressed Files |
| .ACF | Settings Files |
| .ACG | Data Files |
| .ACGD | Uncommon Files |
| .ACGI | Uncommon Files |
| .ACGL | Uncommon Files |
| .ACH | Uncommon Files |
| .ACI | Uncommon Files |
| .ACIDBAT2 | Uncommon Files |
| .ACJ | Uncommon Files |
| .ACK | Uncommon Files |
| .ACL | Misc Files |
| .ACLOCK | Uncommon Files |
| .ACM | Audio Files |
| .ACMB | Uncommon Files |
| .ACMD | Uncommon Files |
| .ACN | Uncommon Files |
| .ACO | Settings Files |
| .ACORN | Uncommon Files |
| .ACP | Audio Files |
| .ACQ | Uncommon Files |
| .ACR | Raster Image Files |
| .ACS | Misc Files |
| .ACSM | Misc Files |
| .ACT | Developer Files |
| .ACTH | Uncommon Files |
| .ACTH2 | Uncommon Files |
| .ACTH3 | Uncommon Files |
| .ACTION | Executable Files |
| .ACTIONNDA | Uncommon Files |
| .ACTIONS | Uncommon Files |
| .ACTIONSCRI | Uncommon Files |
| .ACTPROJ | Uncommon Files |
| .ACU | Uncommon Files |
| .ACUTC | Data Files |
| .ACV | Settings Files |
| .ACW | Settings Files |
| .ACX | Game Files |
| .ACY | Uncommon Files |
| .ACZ | Uncommon Files |
| .AC_ | Uncommon Files |
| .AD | Misc Files |
| .AD! | Uncommon Files |
| .AD0 | Uncommon Files |
| .AD1 | Uncommon Files |
| .AD2 | Uncommon Files |
| .AD3 | Uncommon Files |
| .AD4 | Uncommon Files |
| .AD5 | Uncommon Files |
| Extension | File Description |
| .AD6 | Uncommon Files |
| .AD7 | Uncommon Files |
| .AD8 | Uncommon Files |
| .AD9 | Uncommon Files |
| .ada | Uncommon Files |
| .ADB | Developer Files |
| .ADB1 | Uncommon Files |
| .ADB2 | Uncommon Files |
| .ADBA | Uncommon Files |
| .ADBLOCK | Uncommon Files |
| .ADC | Raster Image Files |
| .ADD | Misc Files |
| .ADDEND | Uncommon Files |
| .ADDENDUM | Uncommon Files |
| .ADDRESS | Uncommon Files |
| .ADDRESSES | Uncommon Files |
| .ADE | Database Files |
| .ADEX | Uncommon Files |
| .ADF | Disk Image Files |
| .ADG | Uncommon Files |
| .ADH | Uncommon Files |
| .ADI | Backup Files |
| .ADINEKIRN | Uncommon Files |
| .ADIUMEMOTI | Uncommon Files |
| .ADIUMEMOTI | Uncommon Files |
| .ADIUMMENUB | Uncommon Files |
| .ADIUMMESSA | Uncommon Files |
| .ADIUMPLUGI | Uncommon Files |
| .ADIUMSCRIP | Uncommon Files |
| .ADIUMSERVI | Uncommon Files |
| .ADIUMSOUND | Uncommon Files |
| .ADIUMSTATU | Uncommon Files |
| .ADJ | Uncommon Files |
| .ADJUST | Uncommon Files |
| .ADK | Uncommon Files |
| .ADL | Uncommon Files |
| .ADM | System Files |
| .ADML | System Files |
| .ADMX | System Files |
| .ADN | Database Files |
| .ADO | Settings Files |
| .ADOBENET | Uncommon Files |
| .ADOC | Uncommon Files |
| .ADOS | Uncommon Files |
| .ADP | Database Files |
| .ADPCM | Uncommon Files |
| .ADQ | Uncommon Files |
| .ADR | Web Files |
| .ADRESSES | Uncommon Files |
| .ads | Uncommon Files |
| .ADSM | Uncommon Files |
| .ADT | CAD Files |
| .ADU | Data Files |
| .ADV | Audio Files |
| .ADVENTURE | Uncommon Files |
| .ADW | Uncommon Files |
| .ADX | Data Files |
| .ADY | Uncommon Files |
| .ADZ | Disk Image Files |
| .AE | Uncommon Files |
| .AE0 | Uncommon Files |
| .AE1 | Uncommon Files |
| .AE2 | Uncommon Files |
| .AE3 | Uncommon Files |
| .AE4 | Uncommon Files |
| .AE5 | Uncommon Files |
| .AE6 | Uncommon Files |
| .AE7 | Uncommon Files |
| .AE8 | Uncommon Files |
| .AE9 | Uncommon Files |
| .AEA | Uncommon Files |
| .AEB | Uncommon Files |
| .AEC | Uncommon Files |
| .AED | Uncommon Files |
| .AEE | Uncommon Files |
