Compress Podcasts to Save Disk Space

My mac is a few years old now, and my hard-drive is getting pretty full, so I was looking for ways to reclaim some disk space. Using DaisyDisk I saw that some of my podcasts use a surprisingly large amount of space, so I wanted to reduce that.

Of course, I could just delete a bunch, and if I ever really want to hear them, I could stream them from the website of the publisher, if there is an archive. But then I rely on a good web connection (which I don’t always have at cafes), they won’t be available on my iPhone, and I can’t track what I’ve already heard.

I wanted to keep everything on my mac, but make each podcast smaller. I wanted to compress the actual files. As with any MP3 file, iTunes can encode (or re-encode) an MP3, reduce the file size by using a lower Bit Rate. The sound quality can get pretty bad, so I wouldn’t do this with music. But for a podcast – basically just people talking – I can deal with it, especially on those that have poor audio anyway.

iTunes does make it easy to re-encode any MP3 (music track or podcast), letting you change the Bit Rate. But it keeps the original version, and it puts the new version into the Music Library – not what I want. It does NOT automatically replace the original, and if it’s a podcast, the new version does not appear in Podcasts. So I found a workflow to solve this, and it’s actually pretty simple.

How to compress podcasts to save disk space

Set Custom Bit Rate

  • in iTunes > Preferences > General, click Import Settings.
  • set “Import Using” to “MP3 Encoder”.
  • set “Setting” to “Custom”.
  • set “Stereo Bit Rate” to something pretty low, maybe 48 or even 32. This is totally subjective.
  • you can also play with the other settings in the MP3 Encoder screen, to fit your taste.

Re-Encode the Files

  • in iTunes > Library > Podcasts, find the podcast I want to compress.
  • select the individual podcast tracks/episodes
  • from the top-menu > Advanced (or right-click menu), select “Create MP3 Version”. This starts the conversion process, and you’ll see a new temporary Playlist in the sidebar, where you can see the progress. It may take a while, depending how many you selected.
  • When the encoding is finished, find the NEW files, in Library > Music > (the artist, based on the Podcast’s Artist field)
  • You can verify that they have the new lower Bit Rate that you set, and that the Size is less than that of the original podcast episode. Do this with Get-Info (command-I), or show those Columns.

Replace the Podcast Files

  • back in Library > Podcasts, in the podcast you’re working on, select one of the tracks/episodes, right-click, and select “Show in Finder”
  • in that Finder window, you should see all the MP3 files that are the ORIGINAL versions of the actual episodes of the Podcast. Select all that you’re changing, and Trash them! But keep this Finder Window OPEN, since you’ll need it soon.
  • (Optional) If trashing your originals makes you nervous, you can first make a ZIP archive of the files. Select them all, right-click and select “Compress X Items” (at least that’s what it says on Snow Leopard). But remember to trash this zip later, after you’re confident that everything worked and you’re happy with the audio quality. If you forget, you won’t save any disk space.. in fact you’ll have lost more space! Move the zip to your desktop, and give it a helpful name. Once you have the zip on the desktop, go Trash those original files (from the prior step).
  • Empty the Trash. This is very important, otherwise iTunes will still see the original files there.
  • in iTunes > Music, find the NEW/converted tracks, under the Artist of the Podcast.
  • Select one, right-click, and Show in Finder.
  • You should now have two Finder windows open – this one with the new files, and the other one that had the original files.
  • in the new Finder window, select all the MP3 files, and DRAG them into the other Finder window, into the Podcast’s Folder exactly where the originals had been before you trashed them.
  • Verify that it worked – in iTunes > Podcasts, find your podcast, and try to play an episode/track. It should work, but sound worse that the original. You can also check the Size or Bit Rate fields, to see the change from the original.

Clean Up

  • During the conversion, remember iTunes put all the new versions into the Music library, but you probably don’t want that, since they’re Podcasts.
  • in iTunes > Music > (the Artist of the Podcast), select all the tracks
  • hit the Delete key
  • EXTREMELY IMPORTANT — Click the “KEEP FILES” button. Otherwise the new files you created will be trashed, which you don’t want. You just want to remove these “tracks” here in the Music Library, but keep the files in the Finder, so they’re still available as a Podcast. IF YOU DON’T SEE THE “KEEP FILES” BUTTON, unselect all the tracks, and just re-select a few at a time. I have no idea why, but it worked.


Congrats. You may have just saved yourself a few gigs of space on your disk.



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