ID3 tags explained
ID3 tags are pieces of data embedded into your podcast episode MP3 files that store information about that audio file, such as the title, artist, year of production, genre and even an embedded image (like your episode or show level artwork) if you're using version 2 of ID3 tagging.
The easiest way to think of these is "information about the file" - like popping a luggage tag onto a suitcase.
This article is relevant to people who add these ID3 tags to audio files manually before uploading to Captivate.
ID3 v2 explained
ID3 tagging has been around for a while but podcasting has its own specific requirements of ID3.
So, ID3 version 2 was released to make sure that podcast players have what they need so that they can download information about your episodes first, so that listeners see this information as they listen to the beginning of your podcast. This is achieved by embedding the ID3 information at the start of the MP3 file.
The IAB states that only version 2 ID3 tags are compliant within its podcast download guidelines. This is because version 1 of ID3 tags forces players to download more data than the listener has listened to and will artificially inflate listening duration and make it seem like a listener has listened to your entire episode, for example.
In order to be IAB compliant, you must be using ID3 v2 tagging when manually tagging your audio files on a computer prior to uploading to Captivate.
The IAB guidelines also state that data equalling 1 minute of audio (minus the size of the ID3 tags) be downloaded in order for that download to count as a valid podcast download, so we recommend keeping your ID3 tags small, in particular any images that you embed using ID3 v2 we recommend keeping smaller than 500kb.