ID3 tags are metadata stored within MP3 files that contains information such as; the title of the podcast or episode, the artist, and an image artwork for the episode. There are two versions of the ID3 tags. ID3v1 contains only basic, text-only, information and it’s placed at the end of the audio file. ID3v2 consist of rich type information like the artwork and they’re placed at the beginning of an audio file. By using ID3v2, a podcast player can display such metadata without having to download the entire file.
Dynamo is not a hosting platform, we can’t either analyze or enforce any size or format specification about ID3, but to provide a better user experience for your listeners we recommend content creators to limit the size of the ID3 metadata to reduce the data transfer and the time it takes for players to be able to playback the first actual audio. The element that accounts for most of the size of the ID3 tags is the embedded artwork, that should be limited to 300KB.