Signatures of Macintosh Files

Summary: What are Macintosh signatures? Where are they stored? What do they mean? How can a file loose its signature? How to restore it?

What Are Signatures?

The Macintosh doesn't use three-byte extensions (or even longer than three bytes, nowadays) to identify the very nature or contents of files, but signatures.
Signatures are strings of eight bytes, four for the creator (the program which created the file) and four for the file type (text, picture, and so on).
See also our Comments for Techies.
The correspondance between signatures and icons is managed by the Finder, for all programs which happened to exist on a volume, in the Desktop file (an hidden system file which is never shown by the Macintosh but exists on every disk). With System 7 and upwards, the Desktop graduated to a double Desktop DB + Desktop DF, for reasons which would led us too far away from our main issue.

Signatures Tables

Here are some of the signatures and corresponding PC extensions we collected (if you want to add or correct something, please feel free to send us an e-mail, we try to update the site frequently).
For those who need to edit the internal table of our Mac-PC transfer programs (MacDisk and MacImage), you will have to note the signature/extension you want to use/exploit and put it in the table displayed by the SignEdit utility (see the manual). If you encounter an atypical file (something not giving the results expected), please check the real signature of a file whose origin doesn't make any doubt, on a Macintosh magnetic volume (see the rightmost column of the display).

Generic Formats

These signatures identify the file type, but not the creator ('????' is a valid creator). They are useful when a program refuses to load a file because the signature is not what it expects and the programmer was too lazzy to look into the file. We give the PC extension when there is a well established one.

`Signature`	`Extension`	Comments
`APPL????`		Application (program)
`EPSF????`	`EPS`	Generic EPS
`JPEG????`	`JPG`	Generic JPEG
`PICT????`	`PCT`	Generic Pict
`PNGf????`	`PNG`	Generic PNG
`TEXT????`	`TXT`	Generic Text
`TIFF????`	`TIF`	Generic TIFF

Specific Formats

These signatures identify both the file type and the creator. Applications other than the creator generally only look at the file type to ascertain whether they can open the file. (The '_' represents a space character.)

`Creator`	`File Typ`	`Extension`	Comments
`8BIM`	`8BIM`	`PSD`	Photoshop 3/4 files
`8BIM`	`8BPS`	`PSD`	Photoshop
`AB65`	`AD65`	`P65`	Pagemaker 6.5
`ALB4`	`ALD4`	`PM4`	Pagemaker 4
`ALB5`	`ALD5`	`PM5`	Pagemaker 5
`ALB6`	`ALD6`	`PM6`	Pagemaker 6
`APPL`	`aust`		Self-extracting archive created by Stuffit
`APPL`	`EXTR`		Self-extracting archive created by Compact Pro
`ART3`	`TEXT`	`AI`	Illustrator 3
`ATMC`	`sfnt`	`OTF`	Open Type font file
`BNHQ`	`TEXT`	`HQX`	BinHex
`BOBO`	`CWWP`	`CWK`	Claris Works text v. 1 to 5
`BOBO`	`WORD`	`CWK`	Claris Works (word processor)
`CARO`	`PDF_`	`PDF`	Acrobat files
`cDRW`	`dDRW`		Claris Draw
`DBSE`	`FTCH`	`FDB`	Image database of Extensis' Portfolio
`DDAP`	`DDFL`		File compressed by Disk Doubler ??
`ddsk`	`devi`	`DMG`	Macintosh disk image
`dPro`	`dDOC`	`MDP`	MacDraw Pro
`FH50`	`AGD1`	`FH5`	Freehand 5
`FHD3`	`FHA3`	`FH3`	Freehand 3
`FMP3`	`FMP3`	`FMP/FP3`	FileMaker Pro
`FXTC`	`EggP`	`AEP`	After Effects' project file
`Gld1`	`PDB_`	`PDB`	Palm OS Database file
`Gld1`	`PRC_`	`PDB`	Palm OS Application file
`inDd`	`inDn`	`IND`	Indesign Document (also *.indd)
`LWFN`	`ASPF`		Adobe Type 1 Font
`MACA`	`WORD`		Mac Write 4.6/5
`MDPL`	`DRWG`		MacDraw II files
`MDRW`	`DRWG`		MacDraw files
`MFL2`	`SPA_`	`FLA`	Fichiers Flash (éditeur)
`MOSS`	`TEXT`	`HTM`	HTML for Netscape Navigator (see A Web Site on a CD for more explanations)
`MSIE`	`TEXT`	`HTM`	HTML for Internet Explorer (see A Web Site on a CD for more explanations)
`MSWD`	`RTF_`	`RTF`	RTF produced by Microsoft Word
`MSWD`	`W6BN`	`DOC`	Microsoft Word 6
`MSWD`	`W8BN`	`DOC`	Microsoft Word 8 (98)
`MSWD`	`WDBN`	`DOC`	Word 3/4/5 Macintosh
`MSWD`	`WTBN`	`DOT`	Word Template
`MV85`	`MD03`	`DIR`	Macromedia Director 8.5
`MV93`	`MD93`	`DIR`	Macromedia Director
`MWII`	`MW2D`		Mac Write II
`nX^2`	`nX^n`		WriteNow 3
`nX^n`	`nX^n`		WriteNow 2
`OMEG`	`TEXT`		Mathematica (all kinds of files)
`MPS_`	`TEXT`	`XML`	XML file (in fact, ????TEXT should do the job)
`PACT`	`CPCT`	`???`	Archive created by Compactor (Pro)
`Pnst`	`PNRA`	`MP3`	Fichier MP3 Real Player
`PPT3`	`SLD3`	`PPT`	Power Point 3
`PPT3`	`SLD8`	`PPT`	Power Point 98
`QSfL`	`QSfl`		Check file of the Symantec AV
`SIT!`	`SIT!`	`SIT`	Archive created by Stuffit
`SIT!`	`SITD`	`SIT`	Archive created by Stuffit
`SSIW`	`WP42`	`WP4`	Wordperfect 4 (saved by WP for the Mac)
`SSIW`	`WP50`	`WP5`	Wordperfect 5 (idem)
`StMI`	`GIFf`	`GIF`	GIF files created by PageMill
`StMI`	`TEXT`	`HTM`	HTML files created by PageMill
`SWF2`	`SWFL`	`SWF`	Flash files
`ttxt`	`TEXT`	`TXT`	SimpleText File
`TVOD`	`jp2_`	`JPG`	JPEG 2 File by QT
`TVOD`	`MooV`	`MOV`	QuickTime movie files (to be used also with other video formats)
`TVOD`	`MPEG`	`MP3`	MP3 file for QuickTime
`TVOD`	`WAVE`	`WAV`	Wave file for QuickTime
`XCEL`	`XLBN`	`XLS`	Excel 1
`XCEL`	`XLS4`	`XLS`	Excel 4
`XCEL`	`XLS5`	`XLS`	Excel 5
`XPR3`	`EPSP`	`EPS`	EPS created by Xpress
`XPR3`	`XDOC`	`QXD`	Xpress (all versions)
`ZIP_`	`ZIP_`	`ZIP`	Zipped archive

Below a more general list of filetype and creator strings we already saw (the '_' represents a space character).

File Types

`Signature`	Comments
`..CT`	Scitex files (put 8BIM as creator if you want that files open directly in Photoshop when you double-click on them on the Mac
`.WAV`	Wave sound file
`.WP4`	PC WP4 file as seen by Wordperfect 2 for the Mac
`.WP5`	PC WP51 file (idem)
`8BIM`	Adobe Photoshop native format
`8BPS`	Transparent
`AB65`	Pagemaker 6.5
`ALB3`	PageMaker 3
`ALB4`	PageMaker 4
`ALB5`	PageMaker 5
`ALB6`	PageMaker 6
`AWDB`	MS-Works database
`AWSS`	MS-Works spreadsheet
`AWWP`	MS-Works word processor file
`BINA`	Text file saved as Word DOS or Word Windows file by Word Mac 5
`CCAD`	Claris CAD
`CrTC`	Project file by Toast 3
`CWWP`	Claris Works text file
`DBSE`	Image database of Extensis' Portfolio
`DCT5`	MS-Word dictionnary
`DDFL`	Disk Doubler data file
`dDOC`	MacDraw Pro file
`dDRW`	Claris Draw File
`DRWG`	MacDraw file
`DWG_`	AutoCAD file
`EggP`	After Effects' project file
`EPSF`	EPS file
`FFIL`	Font Suitcase (Type 1 or True Type)
`ffil`	Display Font
`FH50`	Freehand 5 file
`FHD3`	Freehand 3 file
`F#+D`	Rag Time Classic file
`FMK$`	FileMaker 1 file
`FMP3`	FileMaker Pro file
`GIFf`	GIF files created by PageMill
`GLOS`	MS-Word glossary
`HImg`	Image file created by Toast 3
`inDd`	Indesign Document
`jp2_`	JPEG 2 file
`JPEG`	JPEG file
`lfil`	True Type Font
`LWFN`	Type 1 Font (PostScript font)
`MooV`	QuickTime file
`MP3_`	MP3 file
`Mp3_`	MP3 file
`MPEG`	MPEG file (MPEG1 coding), also MP3
`MPG3`	MP3 file
`MPWd`	MacWrite Pro 1.5 file
`MV93`	Director 5
`MV85`	Director 8.5
`MW2D`	MacWrite II file
`MW2S`	MacWrite II model
`nX^2`	Write Now 3 file
`nX^d`	Write Now 2 file
`PACT`	Compactor data file
`PDF_`	Acrobat files
`PICT`	PICT file
`PNGF`	PNG File
`PNRA`	RealPlayer MP3 file
`R#+A`	RagTime Classic text file
`RTF_`	RTF File
`S#+A`	Rag Time 2 text file
`sfnt`	Open Type font file
`SIT!`	Stuffit Archive
`SITD`	Stuffit Archive
`SLD3`	PowerPoint 3
`SLD8`	PowerPoint 8
`SPA_`	Flash editor file
`SWFL`	Flash player file
`TIFF`	TIFF file
`WAVE`	Wave File
`W6BN`	Mac Word 6
`W8BN`	Mac Word 8 (98)
`WDBN`	Mac Word 3, 4, 5 text file
`WHLP`	MS-Word help file
`WORD`	MacWrite formatted file
`WP42`	PC WP4 file seen by Wordperfect 1 for the Mac
`WP50`	PC WP51 file seen by Wordperfect 1 for the Mac
`WPD0`	Wordperfect 1 text file
`WPD1`	Wordperfect 2 text file
`WPD3`	Wordperfect 3 text file (what happened to the '2'?)
`WPRD`	MS-Word print file
`WTBN`	Word Template
`XDOC`	Xpress file
`XTMP`	Xpress template
`XLBN`	Excel 1 spreadsheet
`XLS_`	Excel 2.2 spreadsheet
`XLS3`	Excel 3 spreadsheet
`XLS4`	Excel 4 spreadsheet
`ZIP_`	Zipped archive

Creator Strings

Please note that '_' represents a space.

`Signature`	Comments
`8BIM`	Adobe Photoshop
`ACAD`	AutoCAD
`AD65`	Pagemaker 6.5
`AGD1`	Freehand 5
`ALD3`	PageMaker 3
`ALD4`	PageMaker 4
`ALD5`	PageMaker 5
`ALD6`	PageMaker 6
`APLS`	??
`aplt`	Applescript
`ART3`	Illustrator 3
`ART5`	Illustrator 5 and later
`ARTY`	Illustrator 1
`ARTZ`	Illustrator 88
`ATMC`	Adobe Type Manager 'C' (Open Type)
`BOBO`	Claris Works
`CARO`	Acrobat Distiller
`CDr3`	Toast v. 3
`cDRW`	Claris Draw
`CPCT`	Compactor (Pro ?)
`DDAP`	Disk Doubler
`dosa`	Unknown PC files
`dPro`	MacDraw Pro
`ERIK`	Finder (Desktop files)
`F#+A`	Rag Time Classic
`FHA3`	Freehand 3
`FMK4`	FileMaker II ?
`FMP3`	FileMaker Pro
`FTCH`	Extensis' Portfolio
`FXTC`	After Effects
`inDn`	InDesign
`MACA`	MacWrite 2.2 and 4.6
`MDRW`	MacDraw
`MDPL`	MacDraw II
`mdos`	DOS file copied by AFE or PC Exchange
`MFL2`	Flash editor
`MOSS`	Netscape (Mozilla)
`MPWR`	MacWrite Pro
`MSWD`	Microsoft Word 3/4/5 for the Mac
`MWII`	MacWrite II
`Nqst`	SoundEdit 16 v.2
`nX^n`	Write Now v. 3
`OMEG`	Mathematica
`Pnst`	RealPlayer
`PPT3`	PowerPoint (all versions)
`PSIP`	Works 1
`PSI2`	Works 2
`R#+D`	Rag Time 3
`S#+D`	Rag Time 2
`SCPL`	SoundApp
`SIT!`	Stuffit
`SSIW`	Wordperfect 1
`StMI`	Adobe PageMill
`SWF2`	Flash player
`ttxt`	SimpleText
`TVOD`	Quick Time
`vgrd`	LaserWriter (Postscript file)
`WPC2`	Wordperfect 2 (3 also)
`XPR3`	QuarkXpress 3
`XCEL`	Excel

More Info for Techies

Signatures are often considered as strings, and the greatest part of information published on signatures is based on this assumption.
However, signatures are handled by programs as 32-bit integers, which means that when you see a filetype coded as 'TEXT', a program will see 0x54455854, or even 0x54584554, depending on whether it is big-endian or little-endian.
This is the explanation of the possible presence of spaces (very frequent) or even of cryptic characters, even of non-printable characters, in the signatures.
Please note also that Apple reserves for its own use all creator strings made only of lower case letters.
Back to Top.

Where are Signatures Stored?

These signatures, against what is often mentionned, even by knowledgeable persons, are not saved in the resource fork of each file, but in the catalog tree (on the disk, in a management structure you will [hopefully] never have to look at).
This mistake finds its origin in the fact that the programs (and only the programs, not the data files) put the icons they use in their resource fork and have to declare (in a bundle resource placed in their resource fork) the signature of the files they intend to manage, so that the Finder knows what to do when the user double-clicks on an icon. Another source of errors comes from the fact that some graphic files save in the resource fork a preview picture of the file (thumbnail to display on the desktop).

Pierre Duhem (ex-Logiciels & Services Duhem)
3, rue Pierre Haret - F-75009 Paris (France) - Tel. (+33) [0]149 700 455
web: http://www.macdisk.com

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