Will adding full tags to my MP3s/AACs make the files bigger? How about lyrics?

This may be a dumb question, but I’ll go ahead and ask it. Say I want to be really anal and fill in absolutely all of the tags on my iTunes library, will that make the files bigger? Or is there a set amount of space allocated to each tag in the music file, which is there whether it’s empty or not? I suspect the latter, but am not sure.

So what about lyrics? The lyrics seem to be stored as a tag too, but the lyrics to a whole song is quite a bit of data, so is that space already accounted for in the file, or will adding lyrics make my files bigger? I currently only have 7MB (yes megabytes) free on my iPod, so this is important to me…

(I know I could go ahead and test it, but my iTunes library is on a different computer, and I’m curious now!)

Yes, adding tags will increase the size of the files (though negligibly in comparison with the space the music itself takes up). The space for metadata isn’t preallocated.

The tags will increase the size of your files - the space is not preallocated. ID3v1 adds 128 bytes to the end of the MP3 file, but is more limited (and cannot store lyrics). ID3v2 is added at the beginning of the file, but has a variable structure and is a variable size. However, developers are encouraged to add ID3v2 tags as padded fields to avoid rewriting the entire file from the beginning when tags are modified. This can add significant amounts of empty data to your MP3 files.

Given that lyrics are just text, they actually do not consume significant amounts of space. Album art stored in ID3v2 tags can add considerable amounts of data to each file, particularly as each song in an album has the same cover art.


Looks like it will take up more space, but it won’t make any significant difference. Most .MP3’s for pop songs are at least 1,000 K bytes (usually more). That’s 1 million characters. Adding even one thousand letters of information would at most increase the file size by 1%.

So don’t stop on account of disc space.

So it looks like I’ve already bloated the files quite a bit by adding album art to everything. Come to think of it, for some albums I scanned in the covers and didn’t even bother to downsize and compress the images that much.

Unless they’re very high quality scans, you’re not adding that much data relative to what’s already in there.

Maybe not, but if the album art is appended to each song on the album, it must add up to quite a few songs’ worth of data over the course of a few hundred albums - and as I said, my iPod is this close to being full.