| .3DB | Futuremark Corporation | Database Files | 3DMark Database | Futuremark 3DMark | Futuremark Corporation |
| .3X5 | Vega-Tek | Database Files | 3x5 Knowledge Base | 3x5 Knowledge Base | Vega-Tek |
| .4DA | 4D, Inc | Database Files | 4th Dimension Database Data File | 4D V17 | 4D, Inc |
| .4DD | 4D, Inc | Database Files | 4th Dimension Database Data File | 4D V17 | 4D, Inc |
| .4ST | 4D, Inc | Database Files | 4th Dimension Database Data File | 4D V17 | 4D, Inc |
| .5D | Microsoft Corporation | Database Files | Microsoft Works File | Microsoft Works | Microsoft Corporation |
| .ABM | Unknown Developer | Database Files | Music Album | Redbana Audition | Redbana |
| .ABS | ComponentAce | Database Files | Absolute Database File | ComponentAce Absolute Database | ComponentAce |
| .ABX | Corel | Database Files | WordPerfect Address Book | Corel WordPerfect X8 | Corel |
| .ACCDB | Microsoft Corporation | Database Files | Access 2007 Database File | Microsoft Visual Studio | Microsoft Corporation |
| .ACCDC | Microsoft Corporation | Database Files | Microsoft Access Signed Package | Microsoft Access | Microsoft Corporation |
| .ACCDE | Microsoft Corporation | Database Files | Access Execute Only Database | Microsoft Access | Microsoft Corporation |
| .ACCDR | Microsoft Corporation | Database Files | Access Runtime Application | Microsoft Access | Microsoft Corporation |
| .ACCDT | Microsoft Corporation | Database Files | Microsoft Access Database Template | Microsoft Access | Microsoft Corporation |
| .ACCDU | Microsoft Corporation | Database Files | Microsoft Access Database Wizard | Microsoft Access | Microsoft Corporation |
| .ACCDW | Microsoft Corporation | Database Files | Microsoft Access Link | Microsoft Access | Microsoft Corporation |
| .ACCFT | Microsoft Corporation | Database Files | Microsoft Access Data Type Template | Microsoft Access | Microsoft Corporation |
| .ADB | Open Source | Database Files | Ada Body File | MacroMates TextMate | MacroMates |
| .ADE | Microsoft Corporation | Database Files | Access Project Extension | Microsoft Access | Microsoft Corporation |
| .ADF | Cloanto Corporation | Database Files | Amiga Disk File | Amiga Forever | Cloanto Corporation |
| .ADN | Microsoft Corporation | Database Files | Access Blank Project Template | Microsoft Access | Microsoft Corporation |
| .ADP | Microsoft Corporation | Database Files | Access Project Extension | Microsoft Access | Microsoft Corporation |
| .AI | Adobe Systems Incorporated | Database Files | Adobe Illustrator File | Adobe Illustrator CC | Adobe Systems Incorporated |
| .ALF | Swiftpage, Inc. | Database Files | ACT! Lookup File | Swiftpage Act | Swiftpage, Inc. |
| .AMB | Bolide Software | Database Files | All My Books Database File | All My Books | Bolide Software |
| .ASK | askSam Systems | Database Files | AskSam Database | askSam | Softonic Corporate |
| .ATO | E2S N.V. | Database Files | ATO Modeler Project | ATO | E2S N.V. |
| .ATV | Sage | Database Files | ACT! Data File | Act! | Swiftpage, Inc. |
| .B2 | Progress Software Corporation | Database Files | Progress Database | ObjectStore | ESW Capital Group |
| .BAK | Various Developers | Database Files | General Backup File | Microsoft SQL Server | Microsoft Corporation |
| .BBT | Procedimientos-Uno, S.L. | Database Files | BTwin Local Database File | BTwin | Procedimientos-Uno, S.L. |
| .BDE | Borland | Database Files | Borland Database Engine | Borland C++ | Micro Focus International plc |
| .BF2 | Management Computer Controls, Inc. | Database Files | BIDFAX 2000 Database File | BIDFAX 2000 | Management Computer Controls, Inc. |
| .BI | Microsoft Corporation | Database Files | Binary File | Microsoft Notepad | Microsoft Corporation |
| .BPL | Autodesk, Inc. | Database Files | AutoCAD Batch Plot File | Autodesk AutoCAD | Autodesk, Inc. |
| .BQS | BQE Software | Database Files | BillQuick Database | BillQuick | BQE Software |
| .BTR | Pervasive Software | Database Files | Btrieve Database File | Pervasive Btrieve Database Manager | Actian Corporation |
| .BTREE | Apple | Database Files | Apple Mac OS HFS+ B-tree File | Apple OS X | Apple |
| .BTV | Apple | Database Files | AppleTalk Desktop Database | macOS | Apple |
| .BTX | SmartWare Corporation | Database Files | SmartWare Backup Text File | SmartWare | SmartWare Corporation |
| .BW1 | Byteworx | Database Files | FMEA Database File | Byteworx FMEA | Byteworx |
| .CAT | Microsoft Corporation | Database Files | Windows Catalog File | Microsoft Windows | Microsoft Corporation |
| .CDB | Nokia | Database Files | Symbian Phonebook Database | Nokia PC Suite | Nokia |
| .CEP | Nomitech | Database Files | CostOS Estimating Project Database File | CostOS Estimating | Nomitech |
| .CKA | Comfort Software Group | Database Files | Comfort Keys Database | Comfort Keys | Comfort Software Group |
| .CKP | Microsoft Corporation | Database Files | SQL Server Checkpoint File | Microsoft SQL Server | Microsoft Corporation |
| .CLF | Ilium Software, Inc. | Database Files | ListPro Database | ListPro | Ilium Software, Inc. |
| .CMD | Microsoft Corporation | Database Files | Windows Command File | Microsoft Notepad | Microsoft Corporation |
| .CND | Melco | Database Files | Melco Condensed Embroidery File | Dakota AlphaSizer | Dakota Collectibles |
| .CRB | BigOven.com | Database Files | BigOven Recipe Database | BigOven Recipe Software | Lakefront Software, LLC |
| .CRP | dBase, LLC | Database Files | dBASE IV Encrypted Database | dBase | dBase, LLC |
| .CRYPT | WhatsApp Inc | Database Files | WhatsApp Encrypted Database File | WhatsApp | WhatsApp Inc |
| .CRYPT12 | WhatsApp Inc | Database Files | WhatsApp Encrypted Database File | WhatsApp | WhatsApp Inc |
| .CRYPT8 | WhatsApp Inc | Database Files | WhatsApp Encrypted Database File | WhatsApp | WhatsApp Inc |
| .CVB | Borland | Database Files | Borland Database Engine | Borland C++ | Micro Focus International plc |
| .CYS | Hot Neuron | Database Files | Clustify Summary Statistics File | Clustify | Hot Neuron |
| .D1 | Progress Software Corporation | Database Files | Progress Database | ObjectStore | ESW Capital Group |
| .D2 | Progress Software Corporation | Database Files | Progress Database | ObjectStore | ESW Capital Group |
| .DAP | SpeedBit | Database Files | Download Accelerator Plus Partial Download | Download Accelerator Plus | SpeedBit |
| .DAT | Unknown Developer | Database Files | Game Data | Dragon UnPACKer | Open Source |
| .DATA | Appricon | Database Files | Analysis Studio Offline Data | Microsoft Excel | Microsoft Corporation |
| .DB | Dwayne Richard Hipp | Database Files | Mobile Device Database File | SQLite | Dwayne Richard Hipp |
| .DB-JOURNAL | Sublime HQ Pty Ltd | Database Files | SQLite Rollback Journal File | Microsoft Notepad | Microsoft Corporation |
| .DB2 | Samsung Electronics | Database Files | Samsung CCTV Video Information File | Samsung SmartViewer | Samsung Electronics |
| .DB3 | Dwayne Richard Hipp | Database Files | SQLite Database File | SQLite | Dwayne Richard Hipp |
| .DB4 | dBase, LLC | Database Files | dBASE IV Data | dBase | dBase, LLC |
| .DBA | PDC (Prolog Development Center) | Database Files | Turbo Prolog Database | Visual Prolog | PDC (Prolog Development Center) |
| .DBC | Microsoft Corporation | Database Files | FoxPro Database File | Microsoft Visual FoxPro | Microsoft Corporation |
| .DBF | dBase, LLC | Database Files | Database File | Microsoft Excel | Microsoft Corporation |
| .DBO | The Game Creators | Database Files | DarkBASIC Object | The Game Creators DarkBASIC Pro | The Game Creators |
| .DBR | Astonsoft | Database Files | DeepBurner Disc Project | DeepBurner | Astonsoft |
| .DBT | Abacus Data Systems | Database Files | AbacusLaw Data File | AbacusLaw | Abacus Data Systems |
| .DBV | multisoft Datentechnik GmbH | Database Files | Database Variable Field | dBase | dBase, LLC |
| .DBW | Ortus Solutions | Database Files | DataBoss Database | DataBoss | Ortus Solutions |
| .DBX | Microsoft Corporation | Database Files | Outlook Express E-mail Folder | Microsoft Outlook Express | Microsoft Corporation |
| .DCB | LexisNexis | Database Files | Concordance Database File | LexisNexis Concordance | LexisNexis |
| .DCT | Microsoft Corporation | Database Files | Dictionary File | QuarkXPress | Quark Software Inc. |
| .DCX | ZSoft Corporation | Database Files | Zsoft Multi-Page Paintbrush File | Adobe Photoshop | Adobe Systems Incorporated |
| .DDL | Oracle Corporation | Database Files | Data Definition Language File | MySQL | Oracle Corporation |
| .DF3 | Omnis Software | Database Files | Omnis Studio Database File Format | Omnis Studio | Omnis Software |
| .DF5 | Omnis Software | Database Files | Omnis7 And Omnis Studio Database File | Omnis Studio | Omnis Software |
| .DF6 | Omnis Software | Database Files | Omnis7 And Omnis Studio Database File | Omnis Studio | Omnis Software |
| .DIA | Spacetornado Software | Database Files | Do It Again Task File | Do It Again | Spacetornado Software |
| .DMO | Wouter van Oortmerssen | Database Files | Cube 2: Sauerbraten Demo File | Cube 2 Sauerbraten | Open Source |
| .DMU | Interscape | Database Files | Musicnizer Database File | Musicnizer | Interscape |
| .DNL | LexisNexis | Database Files | Concordance Database File | LexisNexis Concordance | LexisNexis |
| .DQL | Sapphire Group | Database Files | DataEase Database | DataEase | 4ThePeople Limited |
| .DQY | Microsoft Corporation | Database Files | Excel Query File | Microsoft Excel | Microsoft Corporation |
| .DRI | Microsoft Corporation | Database Files | Microsoft SQL Server Replication File | Microsoft SQL Server | Microsoft Corporation |
| .DSK | Power Software Ltd | Database Files | General Disk Image | PowerISO | Power Software Ltd |
| .DSN | Cadence Design Systems | Database Files | OrCAD Design File | OrCAD PCB Designer | Cadence Design Systems |
| .DXI | ZPAY Payroll Systems, Inc | Database Files | PayWindow Database File | PayWindow | ZPAY Payroll Systems, Inc |
| .DXL | IBM | Database Files | Domino XML Language File | Microsoft Notepad | Microsoft Corporation |
| .E4C | 4Clicks Solutions | Database Files | E4Clicks Project Estimator Import File | e4Clicks Project Estimator | 4Clicks Solutions |
| .ECO | NetManage | Database Files | ECCO Database File | Ecco Pro | NetManage |
| .EDB | Microsoft Corporation | Database Files | Exchange Information Store Database | Microsoft Exchange Server | Microsoft Corporation |
| .EGL | Electronic Gaming Lab | Database Files | EagleCheck Encrypted Database Reference File | EagleCheck | Electronic Gaming Lab |
| .EIT | Yozosoft | Database Files | Yozo Office Template File | Yozosoft Yozo Office | Yozosoft |
| .ELY | Silkwood Software | Database Files | Elyse Database File | Elyse Database | Silkwood Software |
| .EMD | FMJ-Software | Database Files | ABT Extended Module File | Awave Studio | FMJ-Software |
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