System Files
171 extensions
.dll
Dynamic Link Library
.bin
Binary File
.deb
Debian Software Package
.rpm
Red Hat Package Manager
.aes
Advanced Encryption Standard
.bak
Backup File
.arpi
Android Runtime Package Information
.arsc
Android Resource Table
.atn
Adobe Photoshop Action
.000
Generic Data File
.111
Binary File
.509
PKCS#7 Certificate (often .P7B or .P7C)
.7ini
7-Zip Configuration File
.acf
Adobe Color File
.acroplugin
Adobe Acrobat Plugin
.add
AddIn, Office Add-in
.addin
Add-In
.aepkey
Adobe After Effects Keyframe File
.afs3
Android File System v3
.alias
System Alias File
.ani
Windows Animated Cursor
.anx
ActiveX Control
.appxmanifest
App Package Manifest
.apvault
Apple Passwords Vault
.aria2
Aria2 Download File
.ato
Adobe Photoshop Action
.avd
Android Virtual Device
.avg
AVG Antivirus Log File
.aws
Amazon Web Services configuration
.b16
BitTorrent Blocklist
.b2
B2 Backup File
.back
Backup File
.backup
Backup File
.baseconfig
Base Configuration File
.0
Unknown
.0cc
0CC Core Configuration File
.103
Unknown File Type
.104
Unknown File
.106
Unidentified File
.10o
10-Digit Octal Number
.114
Unknown or Obscure File
.129
Unknown Format / Custom Data
.131
Unidentified File
.132
Unknown or Proprietary Binary Data
.136
Unknown or Generic Binary Data
.141
Unknown or Rare File Format
.146
Unknown Format (Potentially Proprietary or Obsolete)
.153
Unrecognized File Format
.156
HP 156 Laser Printer Driver
.157
Unknown
.159
Unusual or Obscure File
.15u
Unknown or Obscure Format
.167
Unknown or proprietary format
.168
Generic Data File
.17
NCSA Mosaic Configuration File
.172
Generic Binary Data File
.18
Unknown or Obscure Format
.19
Unconfirmed or Obscure File
.193
Unknown File Type
.198
Protexis License Protocol File
.199
Unknown Format / Obsolete
.202
Generic Binary Data File
.209
Internal Configuration Data
.219
Uncommon, likely proprietary or custom data container
.235
Unknown or Obsolete Format
.323
Microsoft NetMeeting / Internet Locator Service File
.34
Unknown Format / Generic Data
.3fs
3F Software File
.3~6
Uncommon temporary file
.4ui
4UI User Interface Resource
.5
Unknown Format
.697
Unknown or Obscure File Format
.73l
7-Zip Log File
.73u
Unknown or Obscure Format
.86i
Epson 86i Printer Driver File
.890
Generic Data File
.8bdt
8bitdo Device Tree
.999
Possibly a placeholder or custom file format
.a01
Data file (often backup or archive)
.a2menu
Amiga 2000 Menu File
.a2panel
A2 Panel Configuration File
.aaui
Autodesk Alias UI Layout
.aawdef
Adobe Animate Workspace Definition
.abg
ActiveBuilder Gateway
.abk
ABK File / Arcabit Antivirus Database
.abn
Adobe Binary
.accessor
Accessor File
.aclock
Apple Animation Clock Data
.acs2
Adobe Color Settings File
.acs3
Autodesk Content Service File
.adiumemoticonset
Adium Emoticon Set
.adiumlistlayout
Adium List Layout File
.adiumlisttheme
Adium Theme List File
.adiummessagestyle
Adium Message Style
.adiumplugin
Adium Message Style Plugin
.adm
Active Directory Management (and others)
.adml
Application Description Meta Language
.admx
Administrative Template XML
.adox
Active Directory Object Schema
.aeu
Acoustic Echo Cancellation Unit
.afc
Apple Application Support File
.afploc
Apple Location File
.afs
Andrew File System
.agent
Agent File
.agprefs
Acorn Preferences File
.ahc
ActiveHole Cache File
.ahl
Android Hotswap Layout
.ajm
ActiveX Job Manager
.alb4
Adobe Illustrator Brush Library 4
.ald
ArchLabs Linux Theme
.ald4
Adobe Illustrator CS4 Clipboard
.alf
ALF is not a widely recognized standard file extension with a single, universally accepted full name.
.alf6
Active Accessibility Layout File (version 6)
.allow
Allow File
.anh
Autodesk Helper File
.anl
ANLib Log File
.anr
Android Native Resource
.ansym
Ansys Element Definition File
.antispam5
Anti-Spam Signature File (Version 5)
.aol
AOL Instant Messenger Attachment
.aos
AOS Flight Control System Configuration
.apdetected
Avast Antivirus Detected Malware File
.apfacename
Apple Face Information
.apin
Apple Physics Information
.apm
Android Performance Monitor
.appdata
Application Data File
.applesyncinfo
Apple Sync Info File
.appxsym
APPX Symbol Package
.archcfg
Arch Linux Configuration File
.arg
Arguments File
.asec
Android Secure File
.ashbak
Ashampoo Backup File
.asis
Application Support Information Set
.asrp
Auto-Sleep Recording Profile
.assistant
Assistant File
.assoc
Associated File
.asstrm
Assistant Stream
.attheme
Android Theme File
.audibleprefs
Audible Preferences File
.aus
Aros/AmigaOS Universal System Resource
.auth
Authentication Data File
.automaticdestinations-ms
Automatic Destinations Log
.autoplay
Autoplay Configuration File
.autoreg
Autoregistry File
.avastconfig
Avast Antivirus Configuration File
.avastlic
Avast License File
.avgdx
AVG Disk Index
.avm
AVM Virtual Machine
.awe
AWE (Amiga Workbench Emulator) Resource
.awss
AWS Signer Certificate
.axs
Axon Signal Data
.aza
Azure Active Directory Account Blob
.azs
Azure Storage Blob
.b25
Brute Force Protection 25 File
.b5l
BigFix License File
.b6l
BlackBerry License File
.backup1
Generic Backup File (Version 1)
.backupinfo
Backup Information File
.bak2
Second Backup File
.bak3
Backup File (Version 3)
.bap
Byte Array Packet
.bars
Binary Authorization Response Set
.basebinary
Base Binary File
.bbkeymap
BlackBerry Keymap File
.awl
Aboitiz Wifi Log
.125
Unknown Format
.126
Not commonly associated with a specific standard file format
.155
Uncommon or Obscure Data File
.2
Unknown or Generic Binary File
.89u
Unknown Format
.8u
Unknown/Proprietary Format