229 records

What format is this file, judged by the bytes it starts with?

229 records covering 225 hex signatures, one fact each. Every value is transcribed from the source that states it and carries the sentence it was taken from: 1 source across 1 site, last checked 2026-08-03, due for re-check by 2027-08-03. Every record is listed below, each linking the page its value came from.

Records229

Sources1

Verified2026-08-03

Review by2027-08-03

LicenceCC BY-SA 4.0 (source: Wikipedia)

About this data

The leading bytes (magic number / file signature) that identify a file format, with its usual extension. Answers 'what actually is this file' when the extension is wrong or missing.

The data

Hex signature	Offset	Format	Extension
0 00 00 00 01	0	BOBO
00 00 02 00 06 04 06 00 08 00 00 00 00 00	0
2D 2D 2D 2D 2D 42 45 47 49 4E 20 4F 50 45 4E 53 53 48 20 50 52 49 56 41 54 45 20 4B 45 59 2D 2D 2D 2D 2D	0	<https://en.wikipedia.org/wiki/OpenSSH> OpenSSH private key file
2D 2D 2D 2D 2D 42 45 47 49 4E 20 43 45 52 54 49 46 49 43 41 54 45 2D 2D 2D 2D 2D	0	-----BEGIN CERTIFICATE-----
66 74 79 70 33 67	4	3rd Generation Partnership Project 3GPP and 3GPP2 multimedia files	3gp 3g2
4A 6F 79 21	0	Preferred Executable Format
37 7a BC AF 27 1C	0	7-Zip File Format	7z
8B 45 52 02 00 00 00	0	‹ER␂␀␀␀
46 4F 52 4D ?? ?? ?? ?? 8SVX	0 any	IFF 8-Bit Sampled Voice	8svx 8sv svx snd iff
23 25 4D 6F 64 75 6C 65	23	Modulefile for Environment Modules
42 53 44 49 46 46 34 30	0	bsdiff binary patch
44 43 4D 01 50 41 33 30 50 41 33 30	0	Windows Update Binary Delta Compression file
45 52 02 00 00 00	0	ER␂␀␀␀
52 4E 43 01 52 4E 43 02	0	Compressed file using Rob Northen Compression (version 1 and 2) algorithm
62 6F 6F 6B	0	macOS bookmark format
30 37 30 37 30 31	0	cpio	070701
30 37 30 37 30 32	0	cpio	070702
30 37 30 37 30 37	0	cpio	070707
AC ED	AC	Serialized Java Data
46 4F 52 4D ?? ?? ?? ?? ACBM	0 any	Amiga Contiguous Bitmap	acbmfiff
2A 2A 41 43 45 2A 2A	7	ACE (compressed file format)	ace
41 46 46	0	Advanced Forensics Format	aff
46 4F 52 4D ?? ?? ?? ?? 41 49 46 46	0	Audio Interchange File Format	aiff
62 6F 6F 6B 00 00 00 00 6D 61 72 6B 00 00 00 00	0	macOS file Alias	alias
46 4F 52 4D ?? ?? ?? ?? ANBM	0 any	IFF Animated Bitmap	anbm iff
52 49 46 46 ?? ?? ?? ?? 41 43 4F 4E	0	Animated cursor	ani
46 4F 52 4D ?? ?? ?? ?? ANIM	0 any	IFF CEL Animation	anim iff
60 EA	0	ARJ	arj
30 26 B2 75 8E 66 CF 11 A6 D9 00 AA 00 62 CE 6C	0	Advanced Systems Format	asf wma wmv
2E 73 6E 64	2E	Au audio file format	au snd
4F 62 6A 01	0	Apache Avro binary file format	avro
42 41 43 4B 4D 49 4B 45 44 49 53 4B	0	AmiBack Amiga Backup data file	bac
42 4C 45 4E 44 45 52	42	Blender File Format	blend
42 50 47 FB	0	Better Portable Graphics format	bpg
6D 61 69 6E 2E 62 73	0	main.bs	bs
42 5A 68	0	Compressed file using Bzip2 algorithm	bz2
4D 53 43 46	0	Microsoft Cabinet file	cab
49 53 63 28	0	InstallShield CAB Archive File	cab
52 49 46 46 ?? ?? ?? ?? 43 44 44 41	0	.cda file	cda
43 44 30 30 31	0	CD-i CD image file	cdi
49 54 53 46 03 00 00 00 60 00 00 00	0	MS Windows HtmlHelp Data	chm
80 2A 5F D7	0	Kodak Cineon image	cin
CA FE BA BE	0	<https://en.wikipedia.org/wiki/Java_class_file> Java class file , <https://en.wikipedia.org/wiki/Fat_binary#Apple> Mach-O Fat Binary	class
46 4F 52 4D ?? ?? ?? ?? 43 4D 55 53	0	Musical Score	cmus
C9	0	<https://en.wikipedia.org/wiki/COM_file_(CP/M)> CP/M 3 and higher with overlays	com
49 49 2A 00 10 00 00 00 43 52	0	Canon RAW Format Version 2	cr2
66 74 79 70 63 72 78 43 52	0	Canon RAW Format Version 3	cr3
43 36 34 20 43 41 52 54 52 49 44 47 45 20 20 20	0	Commodore 64 cartridge image	crt
43 72 32 34	0	Google Chrome extension [48] or packaged app [49]	crx
2D 2D 2D 2D 2D 42 45 47 49 4E 20 43 45 52 54 49 46 49 43 41 54 45 20 52 45 51 55 45 53 54 2D 2D 2D 2D 2D	0	PEM encoded X.509 Certificate Signing Request	csr
02 00 5a 57 52 54 00 00 00 00 00 00 00 00 00 00	0	Claris Works word processing doc	cwk
05 07 00 00 42 4F 42 4F 05 07 00 00 00 00 00 00 00 00 00 00 00 01	0	AppleWorks 5 document	cwk
06 07 E1 00 42 4F 42 4F 06 07 E1 00 00 00 00 00 00 00 00 00 00 01	0	AppleWorks 6 document	cwk
A0 32 41 A0 A0 A0	0x165A4	Commodore 64 1541 disk image (D64 format)	d64
A0 33 44 A0 A0	0x61819	Commodore 64 1581 disk image (D81 format)	d81
44 41 41	44	Direct Access Archive PowerISO	daa
50 4D 4F 43 43 4D 4F 43	0	Windows Files And Settings Transfer Repository	dat
72 65 67 66	72	Windows Registry file	dat hiv
DB 0A CE 00	DB	OpenGL Iris Perfomer .PFB (Performer Fast Binary)
44 49 43 4D	128	<https://en.wikipedia.org/wiki/DICOM> DICOM Medical File Format	dcm
52 49 46 58 ?? ?? ?? ?? 46 47 44 4D (big-endian)	0	Adobe Shockwave	dcr
64 65 78 0A 30 33 35 00	0	Dalvik Executable	dex
52 49 46 58 ?? ?? ?? ?? 4D 56 39 33 (big-endian)	0	Macromedia Director file format	dir dxr drx
41 54 26 54 46 4F 52 4D ?? ?? ?? ?? 44 4A 56	0	DjVu document	djv
41 54 26 54 46 4F 52 4D ?? ?? ?? ?? 44 4A 56	0	DjVu document	djvu djv
6B 6F 6C 79	0	Apple Disk Image file	dmg
D0 CF 11 E0	0	DOCFILE	doc
D0 CF 11 E0 A1 B1 1A E1	0	Compound File Binary Format , a container format defined by Microsoft COM. It can contain the equivalent of files and directories. It is used by <https://en.wikipedia.org/wiki/Windows_Installer> Windows Installer and for documents in older versions of <https://en.wikipedia.org/wiki/Microsoft_Office> Microsoft Office . [44] It can be used by other programs as well that rely on the COM and OLE API's. (0xD0CF11E0 visually resembles "DOCFILE". [45] )	doc xls ppt msi msg
53 44 50 58	0	SMPTE DPX image	dpx
44 52 41 43 4F	44	3D model compressed with Google Draco	drc
44 55 43 4b	8	DuckDB database file	duck
e0 01 00 ea	0	Ion (serialization format) binary encoding
45 56 46	0	EnCase EWF version 1 format	e01
2d 45 35 37	0	ASTM E57 3D file format	e57
7F 45 4C 46	0	ELF	elf
52 65 63 65 69 76 65 64 3A	0	Email Message var5	eml
25 21 50 53 2D 41 64 6F 62 65 2D 33 2E 30 20 45 50 53 46 2D 33 2E 30	0	Encapsulated PostScript file version 3.0	eps epsf
25 21 50 53 2D 41 64 6F 62 65 2D 33 2E 31 20 45 50 53 46 2D 33 2E 30	0	Encapsulated PostScript file version 3.1	eps epsf
4C 66 4C 65	4C	Windows Event Viewer file format	evt
45 6C 66 46 69 6C 65	45	Windows Event Viewer XML file format	evtx
45 56 46 32	0	EnCase EWF version 2 format	Ex01
4D 5A	0	DOS MZ executable	exe
5A 4D	0	DOS ZM executable	exe
76 2F 31 01	0	OpenEXR image	exr
45 4D 58 32	0	Emulator Emaxsynth samples	ez2
45 4D 55 33	0	Emulator III synth samples	ez3 iso
46 4F 52 4D ?? ?? ?? ?? 46 41 4E 54	0	Fantavision Movie	fant
46 41 58 58	0	Facsimile Image	fax
46 4F 52 4D ?? ?? ?? ?? FAXX	0 any	IFF Facsimile Image	faxx fax iff
41 47 44 33	0	FreeHand 8 document [50] [51]	fh8
53 49 4D 50 4C 45 20 20 3D 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 20 54	0	Flexible Image Transport System ( <https://en.wikipedia.org/wiki/FITS> FITS ) [41]	fits
66 4C 61 43	0	FLAC	flac
46 4C 49 46	0	Free Lossless Image Format	flif
46 4C 56	0	Flash Video file	flv
46 4F 52 4D ?? ?? ?? ?? 46 54 58 54	0	Formatted Text	ftxt
46 4F 52 4D ?? ?? ?? ?? FTXT	0 any	IFF Formatted Text	ftxt iff
47 53 52 2D 31 35 34 31	0	Commodore 64 1541 disk image (G64 format)	g64
47 49 46 38 37 61 47 49 46 38 39 61	0	Image file encoded in Graphics Interchange Format (GIF)	gif
67 6c 54 46	0	glTF file	glb
47 52 49 42	47	Gridded data (commonly weather observations or forecasts) in the WMO GRIB or GRIB2 format	grib grib2
50 4D 43 43	50	Windows 3.x Program Manager Program Group file format	grp
1F 8B	0	GZIP compressed file	gz
0E 03 13 01	0	Data stored in version 4 of the <https://en.wikipedia.org/wiki/Hierarchical_Data_Format> Hierarchical Data Format .	hdf4 h4
89 48 44 46 0D 0A 1A 0A	0, 512, 1024, 2048, ...	Data stored in version 5 of the <https://en.wikipedia.org/wiki/Hierarchical_Data_Format> Hierarchical Data Format .	hdf5 h5
66 74 79 70 68 65 69 63 66 74 79 70 6d	4	High Efficiency Image Container (HEIC)	heic
00 00 00 18 66 74 79 70 68 65 69 63 00 00 00 00	0	Apple HEIF image file	heif
3F 5F	0	Windows 3.x/95/98 Help file	hlp
4B 43 4D 53	4B	ICC profile	icm
69 63 6e 73	0	Apple Icon Image format	icns
00 00 01 00	0	Computer icon encoded in ICO file format	ico
00 01 00 00	0	Computer icon encoded in ICO file format	ico
5B 5A 6F 6E 65 54 72 61 6E 73 66 65 72 5D	0	Microsoft Zone Identifier for URL Security Zones	Identifier
49 4E 44 58	0	AmiBack Amiga Backup index file	idx
46 4F 52 4D ?? ?? ?? ?? 49 4C 42 4D	0 any	IFF ILBM Interleaved Bitmap Image	ilbm lbm ibm iff
24 53 44 49 30 30 30 31	0	ISO9660 CD/DVD image file	iso
49 73 5A 21	49	Compressed ISO image	isz
2B 2F 76 38 2B 2F 76 39 2B 2F 76 2B 2B 2F 76 2F	0	<https://en.wikipedia.org/wiki/UTF-7> UTF-7 byte order mark for text [31] [30]	\|
4B 57 41 4A	0	Windows 3.1x Compressed File	??_
53 5A 44 44	0	Windows 9x Compressed File	??_
53 5A 44 44 88 F0 27 33	0	Microsoft compressed file in Quantum format	?? _
CE FA ED FE	0	Mach-O binary (reverse byte ordering scheme, 32-bit) [33]	\|
CF FA ED FE	0	Mach-O binary (reverse byte ordering scheme, 64-bit) [33]	\|
DD 73 66 73	0	<https://en.wikipedia.org/wiki/UTF-EBCDIC> UTF-EBCDIC byte order mark for text [31] [30]	\|
FE ED FA CE	0 0x1000	<https://en.wikipedia.org/wiki/Mach-O> Mach-O binary (32-bit)	\|
FE ED FA CF	0 0x1000	Mach-O binary (64-bit)	\|
FE ED FE ED	0	JKS Javakey Store [32]	\|
4c 50 4b 53 48 48 52 48	0	journald log file	journal
00 00 00 0C 6A 50 20 20 0D 0A 87 0A	0	JPEG 2000 format	jp2 j2k jpf jpm jpg2 j2c jpc jpx mj2
FF D8 FF E0 00 10 4A 46 49 46 00 01	0	JPEG raw or in the JFIF or Exif file format	jpg
FF D8 FF DB	0	JPEG raw or in the JFIF or Exif file format	jpg jpeg
00 00 00 0C 4A 58 4C 20 0D 0A 87 0A	0	Image encoded in the JPEG XL format	jxl
37 48 03 02 00 00 00 00 58 35 30 39 4B 45 59	0	KDB file	kdb
2D 2D 2D 2D 2D 42 45 47 49 4E 20 44 53 41 20 50 52 49 56 41 54 45 20 4B 45 59 2D 2D 2D 2D 2D	0	PEM encoded X.509 PKCS#1 DSA private key	key
2D 2D 2D 2D 2D 42 45 47 49 4E 20 50 52 49 56 41 54 45 20 4B 45 59 2D 2D 2D 2D 2D	0	PEM encoded X.509 PKCS#8 private key	key
2D 2D 2D 2D 2D 42 45 47 49 4E 20 52 53 41 20 50 52 49 56 41 54 45 20 4B 45 59 2D 2D 2D 2D 2D	0	PEM encoded X.509 PKCS#1 RSA private key	key
1B 4C 75 61	0	Lua bytecode	luac
04 22 4D 18	0	LZ4 Frame Format	lz4
4C 5A 49 50	0	lzip compressed file	lz
2D 6C 68 30 2D	2	Lempel Ziv Huffman archive file Method 0 (No compression)	lzh
2D 6C 68 35 2D	2	Lempel Ziv Huffman archive file Method 5 (8 KiB sliding window)	lzh
CF FA ED FE	0	Mach-O binary (reverse byte ordering scheme, 64-bit)	macho
6D 61 69 6E 2E 62 73	0	Nintendo Game & Watch image file	mgw
4D 54 68 64	0	MIDI sound file [43]	mid midi
1A 45 DF A3	0	Matroska media container	mkv mka mks mk3d webm
4D 4C 56 49	0	Magic Lantern Video file	MLV
4E 45 53	0	Nintendo Entertainment System image file	nes
4E 45 53 1A	0	Nintendo Entertainment System ROM file	nes
7F 45 4C 46	0	Executable and Linkable Format	none, .axf, .bin, .elf, .o, .out, .prx, .puff, .ko, .mod, .so
4E 55 52 55 49 4D 47 4E 55 52 55 50 41 4C	0	nuru ASCII/ANSI image and palette files	nui nup
4F 41 52 ??	0	OAR file archive format	oar
4F 52 43	0	Apache ORC (Optimized Row Columnar) file format	orc
4F 54 54 4F	4F	OpenType font	otf
43 36 34 46 69 6c 65 00	0	Commodore 64 binary file	p00
65 87 78 56	0	PhotoCap Object Templates	p25 obt
50 41 52 31	0	Apache Parquet columnar file format	par1
50 31 0A	0	Portable bitmap ASCII	pbm
50 34 0A	0	Portable bitmap binary	pbm
78 56 34	0	PhotoCap Template	pbt pdt pea peb pet pgt pict pjt pkt pmt
55 55 AA AA	0	PhotoCap Vector	pcv
25 50 44 46 2D	0	PDF document	pdf
50 32 0A	0	Portable Gray Map ASCII	pgm
50 35 0A	0	Portable Gray Map binary	pgm
85 ?? ?? 03	0	PGP file	pgp
62 70 6C 69 73 74	0	Binary Property List file	plist
89 50 4E 47 0D 0A 1A 0A	0	Image encoded in the <https://en.wikipedia.org/wiki/Portable_Network_Graphics> Portable Network Graphics format	png
50 75 54 54 59 2D 55 73 65 72 2D 4B 65 79 2D 46 69 6C 65 2D 32 3A	0	<https://en.wikipedia.org/wiki/PuTTY> PuTTY private key file version 2	ppk
50 75 54 54 59 2D 55 73 65 72 2D 4B 65 79 2D 46 69 6C 65 2D 33 3A	0	<https://en.wikipedia.org/wiki/PuTTY> PuTTY private key file version 3	ppk
50 33 0A	0	Portable Pixmap ASCII	ppm
50 36 0A	0	Portable Pixmap binary	ppm
25 21 50 53	0	PostScript document	ps
21 42 44 4E	21	Microsoft Outlook Personal Storage Table file	pst
2D 2D 2D 2D 2D 42 45 47 49 4E 20 53 53 48 32 20 4B 45 59 2D 2D 2D 2D 2D	0	<https://en.wikipedia.org/wiki/OpenSSH> OpenSSH public key file	pub
51 46 49	0	qcow file format	qcow
52 49 46 46 ?? ?? ?? ?? 51 4C 43 4D	0	Qualcomm PureVoice file format	qcp
FF 4F FF 51	0	QOI - The “Quite OK Image Format”	qoif
52 61 72 21 1A 07 00	0	Roshal ARchive compressed archive v1.50 onwards	rar
52 61 72 21 1A 07 01 00	0	Roshal ARchive compressed archive v5.00 onwards	rar
3C 72 6F 62 6C 6F 78 21	0	Roblox place file	rbxl
52 53 56 4B 44 41 54 41	0	QuickZip rs compressed archive	rs
73 64 62 66	73	Windows customized database	sdb
53 45 51 36	0	RCFile columnar file format	seq6
21 2D 31 53 4C 4F 42 1F	21	Slob (sorted list of Object storages ) is a read-only, compressed data store with dictionary-like interface	slob
3A 29 0A	0	Smile file	sml
53 4D 53 4E 46 32 30 30	0	SmartSniff Packets File	smsnf200
46 4F 52 4D ?? ?? ?? ?? 53 4D 55 53	0	Simple Musical Score	smus
46 4F 52 4D ?? ?? ?? ?? SMUS	0 any	IFF Formatted Text	smus smu mus iff
4D 49 4C 20	0	"SEAN : Session Analysis" Training file	stg
aa aa aa aa	0	Crowdstrike Channel File	sys
43 36 34 20 74 61 70 65 20 69 6D 61 67 65 20 66 69 6C 65	0	Commodore 64 tape image file	t64
75 73 74 61 72 00 30 30 75 73 74 61 72 20 20 00	257	tar archive	tar
20 02 01 62 A0 1E AB 07 02 00 00 00	0	Tableau Datasource	tde
54 44 45 46	0	Telegram Desktop Encrypted File	tdf
4D 4D 00 2A	0	Tagged Image File Format (TIFF)	tif tiff
4D 4D 00 2B	0	BigTIFF	tif tiff
49 49 2A 00	0	Tagged Image File Format (TIFF)	tif tiff
49 49 2B 00	0	BigTIFF	tif tiff
74 6F 78 33	0	Open source portable voxel file	tox
FF 0A	FF	TrueType font	ttf tte dfont
00 00 FE FF	0	<https://en.wikipedia.org/wiki/UTF-32BE> UTF-32BE byte order mark for text [28] [30]	txt others
0E FE FF	0	<https://en.wikipedia.org/wiki/Standard_Compression_Scheme_for_Unicode> SCSU byte order mark for text [31] [30]	txt others
EF BB BF	0	<https://en.wikipedia.org/wiki/UTF-8> UTF-8 <https://en.wikipedia.org/wiki/Byte_order_mark> byte order mark , commonly seen in text files. [28] [29] [30]	txt others
FE FF	0	<https://en.wikipedia.org/wiki/UTF-16BE> UTF-16BE byte order mark, commonly seen in text files. [28] [29] [30]	txt others
FF FE	0	<https://en.wikipedia.org/wiki/UTF-16LE> UTF-16LE byte order mark, commonly seen in text files. [28] [29] [30]	txt others
FF FE 00 00	0	<https://en.wikipedia.org/wiki/UTF-32LE> UTF-32LE byte order mark for text [28] [30]	txt others
8c 0a 00	0	Unreal Engine Compressed Asset Storage file	ucas
2d 3d 3d 2d 2d 3d 3d 2d 2d 3d 3d 2d 2d 3d 3d 2d	0	Unreal Engine Table of Contents file	utoc
3C 3C 3C 20 4F 72 61 63 6C 65 20 56 4D 20 56 69 72 74 75 61 6C 42 6F 78 20 44 69 73 6B 20 49 6D 61 67 65 20 3E 3E 3E	0	VirtualBox Virtual Hard Disk file format	vdi
63 6F 6E 65 63 74 69 78	63	Windows Virtual PC Virtual Hard Disk file format	vhd
76 68 64 78 66 69 6C 65	76	Windows Virtual PC Windows 8 Virtual Hard Disk file format	vhdxfile
4B 44 4D	0	VMDK files [46] [47]	vmdk
23 20 44 69 73 6B 20 44 65 73 63 72 69 70 74 6F	0	VMware 4 Virtual Disk description file (split disk)	vmdk
43 72 65 61 74 69 76 65 20 56 6F 69 63 65 20 46 69 6C 65	43	Creative Voice file	voc
34 12 AA 55	0	VPK file, used to store game data for some Source Engine games	vpk
4D 53 57 49 4D 00 00 00 D0 00 00 00 00	4D	Windows Imaging Format file	wim swm esd
D7 CD C6 9A	0	Windows Metafile	wmf
77 4F 46 46	0	woff	woff
78 61 72 21	0	eXtensible ARchive format	xar
67 69 6D 70 20 78 63 66	0	XCF (file format)	xcf
58 46 49 52 ?? ?? ?? ?? 33 39 56 4D (little-endian)	0		XFIR????39VM
58 46 49 52 ?? ?? ?? ?? 4D 44 47 46 (little-endian)	0		XFIR????MDGF
58 50 44 53	0	SMPTE DPX image	xpds
2F 2A 20 58 50 4D 20 2A 2F	0	X PixMap	xpm
FD 37 7a 58 5A 00	0	XZ compression utility using LZMA2 compression	xz
46 4F 52 4D ?? ?? ?? ?? 59 55 56 4E	0	YUV Image	yuvn
1F 9D	0	compressed file (often tar zip) using Lempel-Ziv-Welch algorithm	z tar.z
1F A0	0	compressed file (often tar zip) using LZH algorithm	z tar.z
50 4B 03 04 50 4B 05 06 (empty archive) 50 4B 07 08 (spanned archive)	0	zip file format	zip
5A 4F 4F	0	Zoo (file format)	zoo
28 B5 2F FD	0	Zstandard compress	zst

Where this came from

Every record above links the page it was taken from and quotes the sentence that states it. These are the 1 source this dataset was assembled from.

en.wikipedia.orghttps://en.wikipedia.org/wiki/List_of_file_signatures

Machine-readable

data.jsonThe whole dataset — every record with its source URL and source quote.
Open Knowledge Format bundleOne JSON object per line — every record's frontmatter and quoted span exactly as it is held here, in one fetch.
data.csvThe same records as one flat table, for a spreadsheet or a dataframe. The last four columns are the source URL, the quoted sentence it was read from, the date we last checked it, and which columns are our reading rather than the page's words.
How this is made and checkedWhat "verified against source" does and does not mean.

From your own code

Same records, same quotes, without scraping the page: refsource is on PyPI and npm. Each value comes back carrying the URL it was read from and the sentence on that page that states it — .source and .quote sit on the value itself rather than in a side channel, so the checking step is available instead of skipped.

pip install refsource
refsource lookup file-format-signatures format=BOBO

npx -y refsource lookup file-format-signatures format=BOBO

Set your AI assistant up to use this

Two files and no account. Put this in .mcp.json at the root of your project — Claude Code, Cursor, Windsurf, VS Code and Codex all read that file — and your assistant can look this dataset up instead of recalling it. The server is remote, keyless and read-only.

{
  "mcpServers": {
    "referencesource": {
      "type": "http",
      "url": "https://referencesource.org/mcp"
    }
  }
}

Add to Cursor · or, on the command line: claude mcp add --transport http referencesource https://referencesource.org/mcp --scope project

Then one line in the project's CLAUDE.md or AGENTS.md, so the assistant knows when to reach for it:

When a question needs "File format magic numbers", call the referencesource MCP server at https://referencesource.org/mcp (tool `search_records`, dataset_slug `file-format-signatures`) instead of answering from memory — every record it returns carries its source URL and a verbatim quote from that page.

What each tool does, and the servers built over single registers: Connect your AI assistant.

229 records. last verified against source 2026-08-03. due for re-check by 2027-08-03.

Licence. CC BY-SA 4.0 (source: Wikipedia)