how to reduce filesize after deleting unwanted tags?


I deleted a collection of unwantedtags like: ITUNNORM COMMENT, WWWPAYMENT, WWWRADIOPAGE,... on a range of mp3 files.
I noticed that the filesize didn't reduce after deleting the tags. How can I obtain a smaller filesize after deleting tags?

Refresh tags function

try to delete all tags (mark all and hit the red X) and undo ''delete tags'' right after that.


Anyways, unless your files have a high amount of padding, I doubt you will gain anything but a few KB.


Yes that's true, but I'm more concerned about how mp3tag remove tags. It looks now that when I delete an unwanted tag, that the tag is only been overwritten with some spaces or so.
I rather would like to see that the complete tag section is removed and the file been re-written with only the remaining tags without the spaces. This would give the unused space back and a fresh tag without spaces etc...
Or is the technique with an ID3v2 tag so, that the tag section is always written in blocks of 128K or somehing similar? I think I've read something like that a while ago. This also can explain my problem.
I noticed after deleting all tags (v1, v2 & APE) with the red cross and then adding just v2 tags in mp3tag, the file gets an extra 2184 bytes. When I add a v2 tag in Winamp on a 'clean' file I get only 836 bytes extra. Strange both programs adding an ID3v2 tag but mp3tag needs almost 3x the space, what is all in this space then?

@ Noxx: Erasing and undo tags, the my track will remain without changes? The unwanted tags will still be there. Or what do you mean?


The extra space is called padding. It's used because ID3v2 is at the beginning of the file and would require rewriting the whole file whenever you add or remove a single letter. In order to avoid that, some extra space is reserved for possible future changes. As far as I know, there is no recommendation for the padding size so each program can pad to whatever size they like. Mp3tag has a history of changes regarding padding. In some old versions, you were able to set the padding size yourself, then that feature was removed and Mp3tag padded so that the slack space was filled (file systems have a fixed cluster size, so with a cluster size of 4 KB, even if you create a file with 1 byte, it would still use 4 KB on the disk - Mp3tag used to detect the cluster size and adapted the padding size according to that) and recent versions switched back to a constant, in the program hard-coded padding size IIRC.

If an application uses a high amount of padding (let's say 100 KB), if you update the tag with Mp3tag, the tag size will remain the same. By removing the whole tag and rewriting it back using remove and undo, Mp3tag will generate a fresh tag and will most likely use less padding (unless you had a file with no padding at all, a remove and undo will increase the tag size because Mp3tag always adds padding AFAIK).


edit/remove your tags until it's "final'' and then mark all, remove all the tags (x-button) and then undo "remove tags". so you can be sure, that you have ''good'' tags written into the files. with that method you can also remove the lyrics-tag and correct the padding, if you're tagging downloaded music-files.


Okay I think I understand now, with both your explinations.
Still I find it a kind of strange way of working to get you tracks tagged in a optimal way; after some cleaning/adding tags you have to deleted all tags and then undo the deletion to be sure to have an optimal tag usage.
Maybe a special function in mp3tag to optimise the tag space usage would be a nice new feature?


Maybe you could try the little program "ID3Cleanup.exe" from

According to the help it will: USAGE: ID3Cleanup.exe [OPTIONS]... [FILE]...

By default, ID3Cleanup removes empty header frames,
removes image tags with empty images, fixes header size format,
and synchronizes ID3v1 and ID3v2 tags.

    -help, -?           Display this help and exit.
    -test               Check if ID3 tags need cleanup.

    -compact            Removes everything except ID3 tags and MP3 frames.
                        Removes extra bytes inside ID3v2 tag.
    -fixmp3             Removed corrupted mp3 frames (this may introduce skips).
    -remove             Remove all ID3 tags
    -remove1            Remove ID3v1 tags
    -remove2            Remove ID3v2 tags
    -removemm           Remove archived MusicMagic analysis data.

The option "-compact" maybe will do what you want.
But be careful with this!! Several users cleaned their entire collection by mistake!! :w00t:
Try it on some copies first. :sunglasses:


I like to bing this post up again;
I like the idee of removing the padding and the space occupied by erased tags.
But that seems not possible, I also tried the id3cleanup tool but this doesn't find any files that need cleaning even when some tags are removed.
You maybe wondering why I hammering on this, but let me tell;
I'm using MS Synctoy to make backup copies of mp3 folders; in fact it synchronise 1-way to another disc. It works fine and fast, it only copies new or changed files.
So the catch is when I'm erasing unwanted tags with mp3tag, Synctoy doesn't notice any changes and doesn't make a new copys of the changed files. I know I can uncheck the option under Tags: 'to not keep the date of last change' when changing tags in mp3tag. But I rather keep the orignal date of the files so that is not option to me.
I believe more in cleaning up the padding inside the tag, like this the filesize would change and then it will trigger Synctoy to make a copy.
Is this possible?