ID3v1 tags

The first ID3 tag, from 1996. It is exactly 128 bytes, the last 128 bytes of the file, and begins TAG. Its fields are fixed width, so text is cut short at 30 characters, and there is one genre byte. ID3v2 has largely replaced it, but many files carry both.

Layout

Offset	Size	Field	Meaning
0	3	Identifier	`TAG`
3	30	Title	padded with zeros or spaces
33	30	Artist
63	30	Album
93	4	Year	text
97	30	Comment
127	1	Genre	see below; 255 means none

ID3v1.1 changes one thing: when byte 125 is zero and byte 126 is not, the comment is 28 bytes and byte 126 holds the track number. That is how the two versions are told apart.

Offset	Size	Field	Meaning
97	28	Comment
125	1	Zero byte	marks ID3v1.1
126	1	Track	the track number
127	1	Genre

There are no flags, so an unused text field is simply blank. Text is ISO-8859-1 in practice, though nothing in the tag says so.

Genres

The original tag defined 0 to 79; Winamp added 80 to 191, and they are used everywhere. ID3v2’s TCON frame refers to the same numbers. 255 means no genre.

Code	Genre	Code	Genre	Code	Genre	Code	Genre
0	Blues	1	Classic Rock	2	Country	3	Dance
4	Disco	5	Funk	6	Grunge	7	Hip-Hop
8	Jazz	9	Metal	10	New Age	11	Oldies
12	Other	13	Pop	14	R&B	15	Rap
16	Reggae	17	Rock	18	Techno	19	Industrial
20	Alternative	21	Ska	22	Death Metal	23	Pranks
24	Soundtrack	25	Euro-Techno	26	Ambient	27	Trip-Hop
28	Vocal	29	Jazz+Funk	30	Fusion	31	Trance
32	Classical	33	Instrumental	34	Acid	35	House
36	Game	37	Sound Clip	38	Gospel	39	Noise
40	AlternRock	41	Bass	42	Soul	43	Punk
44	Space	45	Meditative	46	Instrumental Pop	47	Instrumental Rock
48	Ethnic	49	Gothic	50	Darkwave	51	Techno-Industrial
52	Electronic	53	Pop-Folk	54	Eurodance	55	Dream
56	Southern Rock	57	Comedy	58	Cult	59	Gangsta
60	Top 40	61	Christian Rap	62	Pop/Funk	63	Jungle
64	Native American	65	Cabaret	66	New Wave	67	Psychedelic
68	Rave	69	Showtunes	70	Trailer	71	Lo-Fi
72	Tribal	73	Acid Punk	74	Acid Jazz	75	Polka
76	Retro	77	Musical	78	Rock & Roll	79	Hard Rock
80	Folk	81	Folk-Rock	82	National Folk	83	Swing
84	Fast Fusion	85	Bebop	86	Latin	87	Revival
88	Celtic	89	Bluegrass	90	Avantgarde	91	Gothic Rock
92	Progressive Rock	93	Psychedelic Rock	94	Symphonic Rock	95	Slow Rock
96	Big Band	97	Chorus	98	Easy Listening	99	Acoustic
100	Humour	101	Speech	102	Chanson	103	Opera
104	Chamber Music	105	Sonata	106	Symphony	107	Booty Bass
108	Primus	109	Porn Groove	110	Satire	111	Slow Jam
112	Club	113	Tango	114	Samba	115	Folklore
116	Ballad	117	Power Ballad	118	Rhythmic Soul	119	Freestyle
120	Duet	121	Punk Rock	122	Drum Solo	123	A capella
124	Euro-House	125	Dance Hall	126	Goa	127	Drum & Bass
128	Club-House	129	Hardcore	130	Terror	131	Indie
132	BritPop	133	Afro-Punk	134	Polsk Punk	135	Beat
136	Christian Gangsta Rap	137	Heavy Metal	138	Black Metal	139	Crossover
140	Contemporary Christian	141	Christian Rock	142	Merengue	143	Salsa
144	Thrash Metal	145	Anime	146	JPop	147	Synthpop
148	Abstract	149	Art Rock	150	Baroque	151	Bhangra
152	Big Beat	153	Breakbeat	154	Chillout	155	Downtempo
156	Dub	157	EBM	158	Eclectic	159	Electro
160	Electroclash	161	Emo	162	Experimental	163	Garage
164	Global	165	IDM	166	Illbient	167	Industro-Goth
168	Jam Band	169	Krautrock	170	Leftfield	171	Lounge
172	Math Rock	173	New Romantic	174	Nu-Breakz	175	Post-Punk
176	Post-Rock	177	Psytrance	178	Shoegaze	179	Space Rock
180	Trop Rock	181	World Music	182	Neoclassical	183	Audiobook
184	Audio Theatre	185	Neue Deutsche Welle	186	Podcast	187	Indie Rock
188	G-Funk	189	Dubstep	190	Garage Rock	191	Psybient

Enhanced TAG extends ID3v1 with longer fields, in a separate block before it.

.MP3 File Format – ID3v1

Layout

Genres