Computer Info

What is Computer File Extension & Its Types?

March 19, 2022

In This Article

What is File Extension?

A file extension is actually a suffix to a computer file name used in an operating system such as Linux, macOS, and Microsoft Windows. Ideally, it can be classified as a specific form of metadata.

A complete file name ideally will comprise the name of the particular file as well as the extension. This extension normally has three to four characters but in some rare cases there can be even one or two characters, and it is typically separated by a dot symbol.

KEY TAKEAWAYS

A file extension in a computer refers to the suffix used in a file name which is actually a type of Meta data, which when added, represents the full name of a file.
A file extension can have one, two, three or four characters after the file name separated by a dot.
A file extension is used to identify the kind of data contained in a file and the operating system uses it to use the right type of app to open the file.
There are different types of file extensions and they vary from one operating system to another.

Understanding Computer File Extension and Its Types

An extension added with the file name typically identifies the file. It facilitates the operating system in understanding the distinctiveness of the file, and the intended use, to some extent.

A file extension helps the operating system as well as the users primarily in two specific ways such as:

It helps to identify the type of data the file contains. Through the file extensions, the users also come to know about the right way to operate files with unfamiliar data and
As for the operating systems, the file extensions help in understanding the apps that are related to the file and use it to open it when you double click on it.

For example, if a file is named as ‘birds_picture.jpg’ it means that it has a ‘jpg’ file extension.

In Windows, when you click on the file, the operating system will search for all those apps that are relevant to JPG files and will open the app first in order to load the file containing images of birds.

And, on the other hand, for a text file named as readme.txt, Windows will know that it is a text file due to the TXT suffix in it and open the file with the default text editor.

Showing the file extensions is not only helpful but it also adds to the security aspect.

This is because without these extensions being shown it would be hard, if not impossible, for a user to tell whether the PDF file they are looking for, for example, is actually a PDF file and not any malicious file.

Different operating systems follow different ways and policies when it comes to showing the file extensions. Here they are.

Windows:

In Windows, file extensions are shown by default. Yes, you can see these even in Windows 7, 8, or 10 though these versions had changed it for some time, but fortunately, things are back to square one.

However, sometimes, the file extensions may not be visible on Windows, which is not an error of the operating system.

No matter whatever is the reason, you can easily turn it back on in Windows. The steps to follow in this case are:

Go to File Explorer window
Click on View, Options, Change folder and search options in that order and
Uncheck the “Hide extensions for known file types” box in the View tab in the Folder Options window.

macOS:

In macOs however, file extensions are not shown by default. This is because the way in which the file extensions used in this particular operating system is not the same as the ways used in Windows.

However, you can make some slight changes so that you can see the file extensions on Mac. The steps to follow in this case are:

Open Finder
Go to Preferences
Click on Advanced and
Click on ‘Show all filename extensions.’

Both macOS and Linux do not rely on file extensions as heavily as Windows does.

Rather, these operating systems use the creator codes and MIME or Multipurpose Internet Mail Extension, which is an internet standard to encode file formats that are used by email programs, to determine the file type they are supposed to deal with.

This information is typically found on the header of the file.

This means that, in macOs and Linux operating systems, you can have a file with no extension in it and it may still be valid, as opposed to Windows operating system.

Therefore, changing or deleting file name extensions should be done according to the operating system that you are using.

For example, if you delete a file name extension in Windows, the operating system will not know what exactly is to be done with the file anymore.

In that case, Windows will ask you which particular app you want to use to open that specific file.

On the other hand, if you delete a file extension in macOS in the Finder, the operating system will add the same right back by using the data available in the MIME type of the file.

However, if you change a file extension, for example ‘birds.jpg’ to ‘birds.txt’ in Windows, the operating system will use an app to open the file which is relevant to the new extension such as Notepad. Two things may happen in this case such as:

One – you get an error message or
Two – the file is opened but is useless being simply a jumbled mess of unrecognizable text.

It is for this reason you are warned by Windows whenever you want to make changes in the file extension and want your confirmation if you still want to proceed with your action.

The same thing happens in the case of macOS and Linux operating systems as well, even though both of these operating systems do not use file extensions exclusively to handle a file.

Typically, a file extension can be changed successfully by using specific types of software programs that are capable of converting it.

File extensions can be given to all types of files such as:

For picture files denoted as .bmp, .gif and more
For music and audio files denoted as .mp3, .wav, and more
For operating system files denoted as .dll, .exe, and more
For text or word processing documents denoted as .doc, .txt, and more
For spreadsheet files denoted as .xls, .xlsx, and more
For web page files denoted as .htm, and more
For image files denoted as .png ,.jpg, and more
For Adobe and other document format files denoted as .pdf.

You will find a more detailed list in the later section.

So, now you may ask what should be the length of a file extension in Windows so that it is considered to be a valid one. Well, it should never be more than the maximum file name character limit of Windows.

This limit may however vary a little bit depending on the version of the Windows operating system you are using.

The file name character limit of Windows 10 is 260, which is the same for Windows 8, Windows 7 and Windows Vista.

However, for Windows XP, it is 255 characters and for Windows 2000, the character limit is up to 254.

Now, finally, take a look at the different types of extensions used against the name of a computer file.

Typically, there can be thousands of different file extensions that can be related with one or more apps, in fact, way too many to include all in one article.

So, here are the ones that are most commonly used along with their respective purposes.

For Archived and Compressed Files:

.?mn – Though not released yet, this file extension will help in opening .arc files for Nintendo
.?Q? – For files compressed by SQ program
7z – For sip compressed file
A – As external file extension for C and C++
AAPKG – For ArchestrA IDE
AAC – For audio files
ACE – For ACE compressed file
ALZ – For ALZip compressed file
APK – For Android package
APPX – For Microsoft application
AT3 – For UMD data compression
ARC – For pre-Zip compressed data
ARC – For Yaz0 compressed Nintendo U8 Archive
ASS or SAS – For video typesetting application
B – For less compressed C and C++ files
BA – For Scifer External Archive Type
BB – For 3D image files made with the Artlantis
BIG – For special files in compression format for Electronic Arts games
BIN – For compressed archive read by CD-ROMs used by Java and extractable by WINRAR and 7-zip
BKF – For Microsoft backup
Blend – For external 3D file format
BMP – For Bitmap Image
BLD – For skyscraper simulator building
CAB – For a library of compressed files
C4 and CALS – For JEDMICS image files
XAML – For exe files for programs like Visual Studio
CLIPFLAIR – For saved state files with XML components
CPT, SEA – For compact pro (Macintosh)
DAA – For Windows only closed format compressed disk image
DEB – For Debian install package
DMG – For Apple compressed or encrypted format
DDZ – For files that can be used only by the daydreamer engine
DN – For Adobe dimension CC file format
DNG – For raw image file format in digital photography
DPE – For package of AVE documents
EGT – For compressed cabinet files
ECAB – For compressed system folders
ESD – For encrypted and compressed WIM file
ESS – For files compressed with EGT compression system
EXE – For Windows app
GBP – For archive index file and data output file
GBS – For OtterUI binary scene file
GIF – For graphics interchange
GZIP – For compressed file
HTML – For HTML code file
IPG – For Apple packages in iPod games
JAR – For zip files used with Java applications
JPG – For image file
JPEG – For image file
LBR – For Lawrence compiler type file
LBR – For library file
LQR – For SQ program-compressed library file
LHA or LZH – Lempel, Ziv, Huffman
LZMA – For LZH chain algorithm compressed file
MHTML – For Mime HTML code file
BIN – For MacBinary
NL2PKG – For NoLimits 2 Package
OAR – For OAR archive
OSG – For compressed osu! live game play archive
OSK – For compressed osu! skin archive
OSR – For compressed osu! replay archive
OSZ – For compressed osu! beatmap archive
PAK – For superior ARC archive
PHP – For PHP code file
PK3 – For Quake 3 archive
PXZ – For compressed layered image file
PY / PYW – For Python code file
RAR – For Rar Archive
RAG, RAGS – For games played on RAGS game engine
RBXL – For Roblox Studio XML and Binary place file
RBXLX – For Roblox Studio XML place file
RBXM – For Roblox Studio XML and Binary model file
RBXMX – For Roblox Studio XML model file
RPM – For Red Hat package or installer file for Fedora and others
SB – For scratch file
SEN – For Scifer internal archive type
SIT – For StuffIt (Macintosh)
SIS/SISX – For Symbian application package
SKB – For Google SketchUp backup file
SQ – For Squish compressed archive
SWM – For split WIM file
SZS – For Nintendo Yaz0 compressed archive
TAR – For group of files packaged as one
TGZ – For g-zip TAR file
TB – For Tabbery virtual desktop tab file
UUE – For all UUE files
VIV – For video games archive format
VOL – For video game data package
WAX – As a ZIP alternative for multiple packaged video files
WIM – For compressed disk image
XAP – For Windows phone app package
XZ – For compressed files based on LZMA/LZMA2 algorithm
Z – For UNIX compressed file
ZIP – As a popular compression format
ZIM – For open file format storing wiki content to use offline and more.

For Physical Recordable Medium Archiving:

ISO – For generic optical media
NRG – For proprietary optical media
IMG – For DOS formatted media
DSK – For floppy disks from other platforms
SDI – For virtual disk functionality
MDS – For images from optical discs
DMG – For Macintosh disk image files
CDI – For DiscJuggler image file
CUE – For CDRWrite CUE image file
CIF – For easy CD creator format
C2D – For Roxio-WinOnCD format
DAA – For PowerISO format
BWT – For BlindWrite 4 image file
B5T – For BlindWrite 5 image file
B6T – For BlindWrite 6 image file and more.

For Computer Aided Design or CAD:

ACP – For virtual architecture file
AMF – For additive manufacturing file
AEC – For DataCAD drawing format
AR – For 3D modeling
ART – For ArtCAM model
ASC – For BRL-CAD geometry file
BIN, BIM – For data design system
BREP – For open CASCADE 3D model
C3D – For its toolkit file
C3P – For Construct3 file
CATDrawing – For CATIA V5 drawing document
CATPart – For CATIA V5 part document
CATProduct – For CATIA V5 assembly document
CATProcess – For CATIA V5 manufacturing document
CGR – For CATIA V5 graphic representation file
CKD, CKT – For KeyCreator CAD Modeling
CO – For 3D modeling and parametric drafting
DGN – For MicroStation design file
DGK – For Delcam geometry
DXF – For ASCII drawing interchange file
DWB – For VariCAD drawing file
DWF – For Autodesk’s web design format
DWG – For drafting and design alliance applications
EASM – For eDrawings assembly file
EDRW – For eDrawings drawing file
EMB – For Wilcom ES designer embroidery file
EPRT – For eDrawings part file
EscPcb, EscSch – For data file by Electro-System (Japan)
ESW – For AGTEK format
EXP – For drawing express format
F3D – For Autodesk Fusion 360 file
FCStd – For FreeCAD package
FM – For FeatureCAM Part File
FMZ – For FormZ Project file
G – For BRL geometry file
GBR – For Gerber file
GLM – For KernelCAD model
GRB – For T-FLEX file
GRI – For AppliCad GRIM-In file for importing wall and roof cladding job data for accounting and business management
GRO – For AppliCad GRIM-Out file for exporting wall and roof cladding data for material and labor
IAM – For Autodesk inventor assembly file
ICD – For IronCAD 2D CAD file
MCD – For monument/headstone drawing file
OCD – For Orienteering CAD file
PIPE – For PIPE-FLO piping system design file
PYT – For Pythagoras file
RVT – For Autodesk Revit project files
RFA – For Autodesk Revit family files
STL – For stereo lithographic data format
TCT – For TurboCAD drawing template
TCW – For TurboCAD Windows 2D and 3D drawing
VC6 – For 2D and 3D drafting
X_B – For Parasolids binary format
XE – For associative 3D modeling
ZOFZPROJ – For ZofzPCB 3D PCB model and more.

For Electronic Design Automation or EDA:

BSDL – For description language
CDL – For Transistor-level for IC design
DEF – For gate-level layout
DSPF – For parasitics of IC design interconnections
EDIF – For vendor neutral gate-level netlist format
FSDB – For analog waveform format
GDSII – For PCB and layout of IC format
HEX – For ASCII coded binary format for memory unload
LEF – For physical abstract of cells for IC design
LIB – For library modeling format
OpenAccess – For design database format using APIs
PSF, PSFXL – For Cadence proprietary format to store waveforms and simulation results
SDC – For synthesis constraints
SDF – For gate-level timings
SPEF – For parasitics of interconnections in IC design
SPI, CIR – For device level commands and netlist for simulation
STIL – For IEEE 1450-1999 standard test patterns for IC
TLF – For logical information and timing about a collection of cells
UPF – For power-domain specifications
V – For Verilog source file
VCD – For digital simulation waveform
VHD, VHDL – For VHDL source file
WGL – For test patterns for IC and more.

For Database:

4DB – For structure file
4DD – For data file
4DIndy – For structure index file
4DIndx – For data index file
4DR – For data resource file (old 4D versions)
ACCDB – For Microsoft database 2007 and later
ACCDE – For compiled Microsoft database 2007 and later
BOX – For Lotus Notes Post Office mail routing database
CHML – For Krasbit encrypted database file
DAT – For DOS basic/Intersystems Caché database file
DTA – For Sage Sterling database file
FRM – For MySQL table definition
GDB – For Borland InterBase Databases
GTABLE – For Google drive fusion table
LDB – For temporary database file
MDE – For compiled Microsoft Access database
MDF – For Microsoft SQL server database
MYD – For MySQL MyISAM table data
MYI – For MySQL MyISAM table index
NSF – For Lotus Notes database
NTF – For Lotus Notes database design template
NV2 – For QW Page NewViews accounting database
ORA – For Oracle table space files
PCONTACT – For WinIM contact file
PDX – For Corel Paradox database management
PRC – For Palm OS resource database
SQL – For bundled SQL queries
REC – For GNU Recutils database
REL – For Sage Retrieve 4GL data file
RIN – For Sage Retrieve 4GL index file
SDF – For SQL compact database file
waData – For Wakanda database data file
waIndx – For Wakanda database index file
waModel – For Wakanda database model file
waJournal – For Wakanda database journal file
WDB – For Microsoft Works database
WMDB – For Windows Media database
Avro – For Big data format for record based attributes
Parquet – For columnar data storage and more.

For Desktop Publishing:

AI – For Adobe illustrator
AVE / ZAVE – For Aquafadas
CDR – For CorelDRAW
CPT – For Corel Photo-Paint
FM – For Adobe Frame Maker
GDRAW – For Google drive drawing
INDD – For Adobe InDesign
MCF – For FotoInsight designer
PDF – For Adobe Reader or Adobe Acrobat
PMD – For Adobe PageMaker
PPP – For Serif PagePlus
PSD – For Adobe Photoshop
PUB – For Microsoft Publisher
QXD – For QuarkXPress and more.

For Document:

0 – For plain text document for licensing
1ST – For plain text document
600 – For plain text document in UNZIP history log
602 – For Text602 document
ABW – For AbiWord document
ACL – For Word AutoCorrect list
ANS – For ANSI text
ASC – For ASCII text
CCF – For Color Chat 1.0
DBK – For DocBook XML sub-format
DOC – For Word document
DOCM – For macro-enabled Word document
DOCX – For Office Open XML document
DOT – For Word document template
DOTX – For Office Open XML text document template
EGT – For EGT universal document
FTM – For fielded text meta
FTX – For fielded text declared
GDOC – For Google drive Document
HTML – For HyperText Markup Language
LOG – For Text log file
MD – For markdown text document
ME – For plain text document preceded by the word
MCW – For Microsoft Word for Macintosh versions 4.0 to 5.1
NEIS – For student record writing Document
ODM – For OpenDocument master document
ODOC – For Synology drive office document
ODT – For OpenDocument text document
OSHEET – For Synology drive office spreadsheet
OTT – For OpenDocument text document template
OMM – For OmmWriter text document
PAGES – For Apple Pages document
PAP – For Papyrus word processor document
QUOX – For question object file format
RPT – For Crystal reports
SE – For shuttle Document
TXT – For Unicode or ASCII plain text file
UOML – For Unique Object Markup Language
WPS – For Microsoft Works document
XHTML– For eXtensible HyperText Markup Language
XML – For eXtensible Markup Language and lots more.

For Financial Data:

IFX – For XML-based specification of financial transactions
OFX – For open standard supported by Microsoft, CheckFree and others
QFX – For proprietary pay-only format of Intuit and more.

For Font Files:

ABF – For Adobe binary screen font
FNT – For bitmapped font of Graphics Environment Manager
FON – For bitmapped font of Microsoft Windows
FOND – For font description resource of macOS and lots more.

For Geographic Information System of GIS:

ASC – For ASCII Point of Interest text file
APR – For ESRI ArcView 3.3 project file
E00 – For ARC/INFO interchange file
GeoJSON – For geographically located object notation data
GeoTIFF – For geographically located raster data
GML – For Geography Markup Language file
GPX – For XML-based interchange format
MXD – For ESRI ArcGIS 8.0 and higher project file
SHP – For ESRI shape file
TAB – For MapInfo Table file
World TIFF – For raster data text file for corner coordinates and others
KML – For XML-based Keyhole Markup Language and more.

For Graphical Information Organizers:

3DT – For meta data of information and ideas of 3D Topicscape stored as concept maps
ATY – For association type export from 3D Topicscape file
CAG –For linear reference system
FES – For exporting fileless occurrences to Windows from 3D Topicscape file
MM – For XML-based FreeMind mind map file
TPC – For exporting inter-Topicscape topic links from 3D Topicscape file and others.

For Graphics Color Palettes and Management:

ACT – For Adobe raw color palette
GPL – For text representation of RGB values and color names
PAL – For Microsoft RIFF palette file
ICC/ICM – For color profile in compliance with the requirement of the ICC and others.

For Raster Graphics:

ART – For America online proprietary format
BLP – For Blizzard Entertainment proprietary texture format
BMP – For Microsoft Windows bitmap formatted image
BTI – For Nintendo proprietary texture format
CR2 – For Canon camera raw formats
CPL – For Windows control panel
DDS – For DirectX texture file
EXIF – For digital camera images format
ICNS – For icons in macOS format
ICO – For icons in Microsoft Windows format
JNG – For single-frame MNG
JPEG, JFIF – For photographic image format
MAX – For ScanSoft PaperPort document
MIFF – For native file format of ImageMagick
OTB – For Nokia specs for black and white images for mobile phones
PC1, PI1 – For compressed Degas picture file of low resolution
PC2, PI2 – For compressed Degas picture file of medium resolution
PC3, PI3 – For compressed Degas picture file of high resolution
PDN – For image file of Paint.NET
PICT, PCT – For Apple Macintosh images
PSB – For Adobe Photoshop large image files
PSD, PDD – For Adobe Photoshop drawing
RAW – For minimally processed digital camera image data
XBM – For X Window system bitmap
XCF – For GIMP image and more.

For Vector Graphics:

3DV – For 3D wireframe graphics
CMX – For CorelDRAW vector image
DP – For PERQ drawing program file
DRAWIO – For offline diagram of Diagrams.net
DXF – For ASCII drawing interchange file
E2D – For 2D vector graphics
EGT – For EGT Vector Draw images
ODG – For OpenDocument drawing
TGAX – For texture format used by Zwift
V2D – For voucher design
VDOC – For vector format used in different software by Future Corporation
VSD – For vector format used by Microsoft Visio
VSDX – For vector format used by MS Visio opened by VSDX Annotator and more.

For 3D Graphics:

3DMF – For QuickDraw 3D Meta file
3DM – For OpenNURBS Initiative 3D Model
3MF – For Microsoft 3D manufacturing format
3DS – For legacy 3D studio model
ABC – For Alembic computer graphics
AC – For AC3D model
ASM – For PTC Creo assembly
BLOCK – For Blender encrypted files
BMD3 – For Nintendo GameCube proprietary model format
CCP4 – For X-ray crystallography voxels
DFF – For RenderWare binary stream
DTS – For Torque Game Engine
FACT – For electric image file
G – For BRL-CAD geometry
GLB – For binary form of glTF
JMESH – For universal mesh data exchange file
LDR – For LDraw model file
LXF – For LEGO digital designer model file
MA – For Autodesk Maya ASCII file
MAX – For Autodesk 3D Studio Max file
MB – For Autodesk Maya Binary file
MPD – For LDraw multi-part document model file
MD2 – For Quake 2 model format
MD3 – For Quake 3 model format
MD5 – For Doom 3 model format
MDX – For Blizzard Entertainment model format
MRC – For cryo-electron microscopy voxels
PLY – For Polygon file format
PRT – For PTC Creo part
POV – For POV-Ray document
RWX – For RenderWare object
SIA, SIB – For Nevercenter Silo object
SKP – For Google Sketchup file
SLDASM – For SolidWorks assembly document
SLDPRT – For SolidWorks part document
SMD – For Valve Studiomdl data format
USDA – For human readable text of Universal Scene Description format
USDC – For binary format of Universal Scene Description
USDZ – For Universal Scene Description zip
VRML97 – For Virtual Reality Modeling Language
X – For DirectX 3D model
ZBMX – For Mecabricks Blender add-on and more.

For Links and Shortcuts:

ALIAS – For macOS
JNLP – For Java applets over internet
LNK – For binary-format shortcuts in Windows 95 and later
APPREF-MS – For file shortcut formats of ClickOnce
DESKTOP – For Desktop entry on Linux Desktop environments
NAL – For ZENworks Instant shortcuts
URL – For internet and bookmark shortcuts in Microsoft Windows
WEBLOC – For internet and bookmark shortcuts in macOS
SYM – For symbolic link and others.

Mathematical

MML – For Mathematical Markup Language
ODF – For OpenDocument math formula and a few others.

For Executable Files, Object Codes, Dynamically Linked and Shared Libraries:

.8BF files – For plugins of some photo editing programs
.a – For objective C static native library
a.out – For traditional UNIX object format
APP – For folder containing program resources and codes on macOS systems
BAC – For executable image for the RSTS/E system
BPL – For Win32 PE file created with C++Builder or Borland Delphi
BUNDLE – For Macintosh plugin that holds data files, executable codes, and folders for it
CLASS – For using in Java
COM – For commands used in CP/M and DOS
DLL – For OS/2 and Windows library used to store data, code, and resources
EAR – For Java enterprise apps
IPA – For Apple IOS app executable file
JEFF – For execution from static memory directly
JAR – For Java class files
MACH-O – For native format of Mac-based systems
NLM – For native binaries of 32-bit for Novell’s NetWare Operating System version 3 or higher
O– For object files unlinked from the compiler directly
RLL – For storing program resources in Microsoft operating systems
S1ES – For executable used by its learning system
SO – For typically ELF shared library
VAP – For native binaries of 32-bit for Novell’s NetWare Operating System version 2 and others
WAR – For Java web apps archives
XBE – For Xbox executable
XAP – For Windows phone package
XEX – For Xbox 360 executable
LIST – For variable list and more.

For Page Description Language:

DVI – For formats independent of devices
EGT – For universal documents to store CSS type styles
SNP – For Microsoft Access report snapshots
XSL-FO – For formatting objects
XSLT, XSL – For XML style sheet
TPL – For web template and more.

For Personal Information Manager:

MSG – For task manager of Microsoft Outlook
ORG – For PIM package of Lotus Organizer
ORG – For Emacs Org-Mode Mind manager
PST, OST – For email communication over Microsoft Outlook and more.

For Presentation:

GSLIDES – For Google drive presentation
KEY, KEYNOTE – For Apple Keynote presentation
NB – For Mathematica slideshow
NBP – For Mathematica Player slideshow
ODP – For OpenDocument presentation
OTP – For templates of OpenDocument presentation
PEZ – For Prezi desktop presentation
POT – For Microsoft PowerPoint template
PPS – For Microsoft PowerPoint show
PPT – For Microsoft PowerPoint presentation
PPTX – For Open XML Office presentation
PRZ – For Lotus Freelance graphics
SHOW – For Haansoft presentation software document
SHW – For Corel presentations slideshow creation
SLP – For Logix-4D Manager Show control project
THMX – For Microsoft PowerPoint theme template
WATCH – For Dataton Watchout presentation and more.

For Scientific Data Exchange:

FITS – For astronomy
SILO – For visualization storage format
SPC – For spectroscopic data
EAS3 – For structured data in binary format
EOSSA – For space situational awareness format
OST – For extensible images with pure or related data
CCP4 – For x-ray crystallography voxels
MRC – For cryo-electron microscopy voxels
HITRAN – For spectroscopic data alteration in one IR or optical line in the ASCII file
ROOT – For platform independent, hierarchical, compressed, binary format
SDF – For platform independent binary data I/O format
MYD – For LED measurements software file
CSDM – For correlated and multi-dimensional datasets
HDR, H4 or H5 – For hierarchical data format
GRIB – For weather model data
BUFR – For weather observation data
PP – For weather model data of the UK Met Office
NASA-AMES – For observation data in simple text format
CML – For Chemical Markup Language
CTAB – For Chemical table file
JCAMP – For atomic and molecular data
GRAPH6, SPARSE6 – For adjacency matrices in ASCII encoding
AB1 – For chromatogram files used in DNA sequencing
ACE – For a sequence assembly format
ASN.1 – For data representation of nucleotide, genomes, protein sequences, and more
BED – For extensible display format to describe genes and other aspects of DNA sequences
CAF – For sequence assembly
CRAM – For compressed file storing biological sequences aligned with a reference sequence
DDBJ – For database records of peptide and nucleotide sequences of DDBJ database
EMBL – For database records of peptide and nucleotide sequences of EMBL database
FASTA – For sequence data
FASTQ – For sequence data with quality
GFF – For describing genes and other features of RNA, DNA, and protein sequences
GTF – For information about gene structure
MAF – For storing multiple alignments for whole-genome to whole-genome comparisons
NCBI ASN.1 – For structured format for protein and DNA data used at National Center for Biotechnology Information
NEXUS – For mixed information and data of genetic sequence in a block structured format
NeXML– For phylogenetic trees in XMl format
NWK – For Newick tree format
PDB – For biomolecule structures
SBML – For Systems Biology Markup Language
SCF – For storing data from DNA sequencing
SRA – For storing high-output DNA sequence data by the National Center for Biotechnology Information Short Read Archive
STOCKHOLM – For representing various sequence alignments
SWISS-PROT – For representing Swiss-Prot database records for protein sequences
VCF – For the collection of lists and notes of the collection of human variants
DCM – For digital imaging and communications in medicine
ECGML – For markup language of electro-cardiogram data acquirement and analysis
EDF/EDF+ – For European data format
FEF – For exchange format of Vital signs
GDF v1.x – For version 1.x of general data format of biomedical signals
GDF v2.x – For version 2.x of general data format of biomedical signals
MFER – For encoding rules of medical waveform
SCP-ECG – For communication protocol standard of computer assisted electrocardiography
SIGIF – For digital signal interchange in neurophysiology
HL7) – For electronic exchange of health information
xDT – For data exchange of medical records and lots more.

For Programming Scripts and Languages:

AS – For Adobe Flash ActionScript file
BAT, BTM, CMD – For batch file
BAS – For QBasic file
CPP – For C++ file
CS – For C# file
ERB – For Ruby on Rails Script file
IBI – For Icarus script
M – For Mathematica package file
NUC – For compiled script
NUD – For C++ External module written in C++
PDE – For processing or programming language
PHP – For PHP file
PHP? – For PHP version number
PL – For Perl
PM – For Perl module
PS1 – For Windows PowerShell shell script
PS1XML – For Windows PowerShell format and type definitions
PSC1 – For Windows PowerShell console file
PSD1 – For Windows PowerShell data file
PSM1 – For Windows PowerShell module file
PY, PYO – For Python
PYC – For Python byte code files
R – For R scripts
R – For REBOL scripts
RB – For Ruby
RS – For Rust programming language
SB2/SB3 – For Scratch
SCPT – For Applescript and others.

For Security Keys and Certificates:

GXK – For private, authorized, and confidential email communications
NSIGN – For custom format public key
X.509 – For notable encoding rules
PKCS#7 – For certificate revocation lists
PKCS#12 – For storing public keys and public certificates
PEM – For storing encoding rules in Base 64 format
AXX – For encrypted file
EEA – For protecting email attachments
TC – For virtual encrypted disk container
KODE – For encrypted file
NSIGN – For encrypted private key
BPW – For encrypted password file
KDB – For KeePass 1 database
KDBX – For KeePass 2 database and more.

For Non-audio Signal Data:

ACQ – For AcqKnowledge format
ADICHT –For LabChart format
BKR – For EEG data format
BDF, CFG – For configuration of Comtrade data
CFWB – For chart data format
DAT – For raw data file
FEF – For vital sign exchange format
GDF – For general data of biomedical signals
SAC – For earthquake seismology data
SEED, MSEED – For sensor metadata and seismological data
SEGY – For reflection seismology data and more.

For Sound and Music:

8SVX – For Commodore-Amiga 8-bit sound
16SVX – For Commodore-Amiga 16-bit sound
AIFF, AIF, AIFC – For audio interchange format
AU – For simple audio file
RAW – For raw samples with no header or sync
WAV – For Microsoft Wave
RA, RM – For RealAudio format
OFR, OFS, OFF – For OptimFROG
THD – For Dolby TrueHD
TTA – For free lossless audio codec
WV – For WavPack
AC3 – For Dolby Digital tracks
AMR – For UMTS and GSM based mobile phones
MP1 – For MPEG Layer 1
MP2 – For MPEG Layer 2
MP3 – For MPEG Layer 3
SPX – For Speex
OTS – For audio file with more data and better compression
VOX – For Dialogic ADPCM low sample rate digitized voice
VOC – For output format for RCA audio recorders
MOD – For melody and sample modules of Soundtracker and Protracker
XM – For fast tracker module
MEI – For encoding all musical notations
MUS, MUSX – For finale sheet music file
MXL, XML – For Music XML standard sheet music exchange
SIB – For Sibelius sheet music file
CUST – For custom sound format
MNG – For background music for creatures’ games
RAM – For audio metafile of RealAudio files only
XPL – For HDi playlist
ZPL – For Xbox music playlist from Microsoft
M3U – For playlist of multimedia
ATMOS, AUDIO, METADATA – For files related to Dolby Atmos mastering and rendering
AUP – For Audacity project file
AUP3 – For Audacity 3.0 project file
CEL – For Adobe Audition loop file
CAU – For Caustic project file
CPR – For Steinberg Cubase project file
DRM – For Steinberg Cubase drum file
SES – For Adobe audition multi track session file
SFK – For Sound Forge waveform cache file
SFL – For Sound Forge sound file
SNG – For MIDI sequence file
STF – For all tracks, samples, patches, and settings
DVR-MS – For Windows Media Center recorded television format and lots more.

For Computer Program Source Codes:

BAS – For BASIC, Visual Basic and more
BB – For Blitz Basic
C – For C source
CLS – For Visual Basic class
COB, CBL – For COBOL source
CPP, CC, CXX, C, CBP – For C++ source
CS – For C# source
D – For D source
DBPro123 – For Dark BASIC professional project
E – For Eiffel source
EGT – For EGT Asterisk source
FOR, FTN, F, F77, F90 – For FORTRAN source
FRM – For Visual Basic form
FRX – For Visual Basic binary form stash file
FTH – For Forth source
GED – For Game Maker extension editable file version 7.0
GM6 – For Game Maker editable file version 6.x
GMD – For Game Maker editable file version 5.x
GMK – For Game Maker editable file version 7.0
H, HPP, HXX – For C/C++ header file
I – For SWIG interface file
INC – For Turbo Pascal included source
JAVA – For Java source
L – For Lex source
M – For objective-C source
M – For MATLAB
M – For Mathematica
M4 – For m4 source
ML – For standard ML and OCaml source
MSQR – For M² source
N – For Nemerle source
P – For Parser source
PAS, PP, P – For Pascal source
R – For R source
RED – For Red source
REDS – For Red system source
RESX – For .NET applications resource file
RKT, RKTL – For Racket source
SCM – For Scheme source
SKB, SKC – For Sage Retrieve 4GL common area
SKD – For Sage Retrieve 4GL database
SKF, SKG – For Sage Retrieve 4GL file layouts
SKI – For Sage Retrieve 4GL instructions
SKK – For Sage Retrieve 4GL report generator
SKM – For Sage Retrieve 4GL menu
SKO – For Sage Retrieve 4GL program
SKP, SKQ – For Sage Retrieve 4GL print layouts
SKS, SKT – For Sage Retrieve 4GL screen layouts
SKZ – For Sage Retrieve 4GL security file
SLN – For Visual Studio solution
VAP – For Visual Studio analyzer project
VB – For Visual Basic.NET source
VBP, VIP – For Visual Basic project
VBPROJ – For Visual Basic .NET project
VCPROJ – For Visual C++ project
VDPROJ – For Visual Studio deployment project
XQ – For XQuery file
Y – For Yacc source
123 – For Lotus 1-2-3
AB2 – For Abykus worksheet
AB3 – For Abykus workbook
AWS – For Ability Spreadsheet
BCSV – For Nintendo proprietary table format
CSV – For comma-separated values
GSHEET – For Google drive spreadsheet
LCW – For Lucid 3D
ODS – For OpenDocument spreadsheet
OTS – For OpenDocument spreadsheet template
QPW – For Quattro Pro spreadsheet
SDC – For StarOffice StarCalc Spreadsheet
TAB – For tab delimited columns or tab-separated values
VC – For Visicalc
WK1 – For Lotus 1-2-3 up to version 2.01
WK3 – For Lotus 1-2-3 version 3.0
WK4 – For Lotus 1-2-3 version 4.0
WKS – For Lotus 1-2-3 and Microsoft Works
WQ1 – For Quattro Pro DOS version
XLK – For backup of Microsoft Excel worksheet
XLS – For sheet in Microsoft Excel 1997 to 2003
XLSB – For binary workbook of Microsoft Excel
XLSM – For Microsoft Excel macro-enabled workbook
XLSX – For Office Open XML worksheet sheet
XLR – For Microsoft Works version 6.0
XLT – For Microsoft Excel worksheet template
XLTM – For Microsoft Excel macro-enabled worksheet template
XLW – For Microsoft Excel version 4.0 worksheet workspace and more.

For Video:

AAF – For rendering information and edit decisions
3GP – For cell phones video format
ASF, AVI – For using any form of compression container
BIK – For video compression system of RAD game tools
CAM – For log file of MSN webcam
COLLAB – For Blackboard Collaborate session recording
DAT – For video standard data
FLV – For encoded Flash video to run in flash animation
FLA – For Adobe Flash
SOL – For Adobe Flash shared objects
STR – For video stream of Sony PlayStation
M4V – For Apple’s video container file
MKV – For using any video format with other content format
MNG – For simple animation of JPEG and PNG objects
MOV – For using any form of compression
MXF – For standard wrapper format for AV material
NSV – For streaming video content over internet
SMI – For SAMI Caption file
YUV – For raw video format
WebM – For web-based video file format using HTML5
SUF – For camera configuration file of Sony
MOTN – For Apple Motion projects
IMOVIEMOBILE – For iMovie project files for iOS users
VPROJ – For VSDC Free Video Editor project files and more.

For Web Page:

DTD – For defining document type
MAF – For archive based web file on ZIP
ASP – For active server page of Microsoft
ASPX – For Microsoft Active Server Page.NET
ADP – For dynamic page of AOLserver
BML – For Better Markup Language templates
CFM – For ColdFusion
iHTML – For Inline HTML
LASSO – For files based on Lasso programming language and more.

For Different Web Standard Formats and Markup Languages:

ATOM – For syndication
EML – For desktop email clients
JSONLD – For linked data serialization based on JSON
KPRX – For workflow definition serialization based on XML
PS – For test automation scripts serialization based on XML
METALINK – For listing metadata about downloads
RSS – For syndication
MARKDOWN or MD – For plain text formatting syntax
SE – For lightweight markup language and others.

For Generic Files:

These file extensions are reused often with no particular format or different formats by several programs.

BAK – For binary files with different backup formats
BIN – For binary data such as executable code memory dumps
DAT – For proprietary data file
DSK – For different disk storage images
RAW – For unprocessed data
CNF, CONF, CFG – For software-specific text files
LOG – For text files and occasional binary files
DIFF – For text file differences
!UT – For incomplete uTorrent download
CRDOWNLOAD – For incomplete Google Chrome download
OPDOWNLOAD – For incomplete Opera download
PART – For incomplete Transmission or Mozilla Firefox download
PARTIAL – For incomplete Microsoft Edge or Internet Explorer download
TEMP – For raw data in temporary files and more.

For Others:

AXD – For cookies found in temporary internet folder
BDF – For raw data of unallocated space from recovered blocks on a hard drive
CEX – For PDM vault file of SolidWorks Enterprise
COL – For proprietary collision file of Nintendo GameCube
CREDX – For DAT file of CredX
DDB – For generated codes of voice of Vocaloid singers
DDI – For Vocaloid phoneme library in different languages
DUPX – For database management tool file of DuupeCheck
FTM – For data file of Family Tree Maker
FTMB – For backup file of Family Tree Maker
GED – For exchanging genealogy data between diverse genealogy software
HLP – For Windows help
IGC – For flight tracks in the approved format of FAI downloaded from different GPS devices
INF – For installing device drivers in Windows
KTR – For Kettle transformation projects or Hitachi Vantara Pentaho data integration file
LNK – For hyperlinks to executables format in Microsoft Windows
LSM – For programs or script file to create special effects by using layered .jpg
NARC – For Nintendo DS games archive format
PA – For assigning sound effects to the materials in KCL files
PIF – For running MS-DOS programs in Windows
POR – For portable SPSS files that are readable by PSPP
PXZ – For exchanging media elements by compressed file using PSALMO
RISE – For information model evolution
SCR – For screen saver file in Windows
TOPC – For SEO project files of TopicCrunch containing domain, keywords, and search engine settings according to ASCII
XLF – For extensible LADAR format of Utah State University
XMC – For assisted contact lists based on XML and used in schools and kindergartens
ZONE FILE – For DNS zone file
ANI – For animated cursor
CUR – For cursor file
SMES – For configuration file of Hawk’s Dock and more.

As said earlier, this is just a modicum of the file extensions. Factually, there are thousands of them available out there and used.

There are several other file extensions for different video game data and storage, and virtual machines along with other generalized files.

If you want to know about all those names and their meaning, look for articles that tell about the file name extensions and their full forms.

Finally, a word of caution: Play safe when you open files and do not open any that comes from unknown or unreliable sources.

Be informed that there are lots of file types and extensions out there that may be potentially risky and dangerous because these executable files can run specific codes when you open them.

Conclusion

The computer file extensions are the identifier of a file that the operating systems use to recognize it.

As this article points out, there are different types of file extensions that are of utmost importance and therefore should not be changed.