FCP X: Delete Generated Media

Posted on by Larry

Logo-FCPX.jpgFinal Cut Pro X handles render files and other generated media differently than Final Cut Pro 7. Let me explain.

Definition: Generated Media. Media created by Final Cut. This includes render files, optimized media and proxy media.


FCP 7 did not have the concept of optimized or proxy media. Yes, AVCHD files would be converted using Log and Transfer to ProRes 422, but, in general, you edited what you shot.

When it comes to render files, Final Cut 7 and Final Cut X both create render files for transitions, titles and effects, including color correction. However, once those files are created, the differences begin.

In Final Cut Pro 7, when you deleted or trimmed a clip to which render files were attached, those render files were immediately deleted. The advantage to this was that you never had render files hanging around not being used, but taking up storage.

While this saves a storage space, it also meant that you were often re-rendering clips that had already been rendered.


FCP X allows creating both optimized and proxy media for a wide variety of reasons, but, in general, they boil down to two:

As a fast estimate, assume that one minute of optimized media takes 1 GB to store, while one minute of proxy media takes about 250 MB to store.

However, FCP X significantly differs from from FCP 7 when it comes to render files.

In FCP X, render files are not deleted when you decide to remove a clip from the Timeline, or trim a portion of a clip, that has already been rendered. Instead, Final Cut Pro X hangs on to render files so that if you add that clip back to the timeline, or readjust the trim to a clip, it instantly reattaches the render files, so that no new rendering needs to be done; assuming there were no changes to the clip since the last time it was used.

NOTE: If Final Cut needs to re-render a clip, any existing render files for the frames being re-rendered are deleted.



Apple made it easy for us to manage generated media using File > Delete Generated Library/Event/Project Files. Final Cut determines which menu to display based upon what you have selected before going to the File menu.


In all three cases, this dialog appears.

If you realize, too late, that you should not have deleted either the optimized or proxy files, re-create them by selecting the clips you want to use in the Browser and choose File > Transcode Media.  Again, all you lose is time.


Give the amount of storage media often required, deleting generated files sounds like a good idea. In general, though, I don’t worry about this, unless I’m desperately short on storage space.

However, I DO delete generated media when archiving a project. There’s no reason to archive files that Final Cut can easily recreate when it needs them in the future.

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33 Responses to FCP X: Delete Generated Media

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  1. Richard says:

    In FCPX 10.14. When animating still photos for example, (ken burns or keyframes), when I change a transition between 2 clips and re-render, there is always a jump cut so to speak because some frames are re-rendered and some are not. How do I re-render the entire clip when FCPX does not want to.

  2. Joe Burford says:

    I’m encountering exactly the same problem. I edit wedding photographs in slideshow films and frequently encounter rendering problems with FCPX. Very frustrating when i’ve left it rendering overnight!
    Many thanks in anticipation,

    Joe Burford

    • Larry says:

      Joe & Richard:

      My guess, as I can’t see your systems, is that your still images are too big. Try to keep them below 5,000 pixels on a side. Also, be sure they are RGB and not some other color space. Finally, DPI is not relevant, it is the total number of pixels that matters.


  3. Jim says:

    Realizing these comments are a year old…I just ran into this with a series of stills, but also generated titles and lower thirds. It’s not related to image size. I found that when using the video animation transparency handles to generate clip fades, then making any sort of duration change in the timeline upstream of those clips, but for a duration change less than the length of the clips, triggers only a partial re-render, corrupting the total clip. My fades either didn’t work or were doubled. Doing something in video animations that triggered a complete re-render of the clip solved the problem, but is impractical. I reported the issue to Apple, their Pro App guys replicated the problem on their computers in two different OS versions. They acknowledged this as a bug, and turned it over to engineering. The work-around is to ditch your render files then re-render everything. Not spiffy, but gets it done.

  4. Marc says:

    Hi, Larry, I recently updated FCP to 10.4.1. Now, every time I try to Delete Generated Event Files (no matter whet Library I’m using), FCP crashes. I don’t know if this is related to the the update or if something has gone wrong of got corrupted. I have reset the FCP Preferences but that has no effect. Got any ideas on this?

    • Larry says:


      Hmmm…. While I haven’t seen this personally, I am getting other reports of strange behavior in the 10.4.1 update. Whenever you get crashes, I always recommend contacting Apple Support. Apple can’t fix a problem if they don’t know about it.


  5. Landon says:

    I have encountered the same problem as Marc. fcpx will crash as soon as I try and delete render files. Running 10.4.2. What folders within library contents contain the render files? I will just delete them myself, and then fcpx can render what it needs.

    • Larry says:


      I really don’t recommend trashing files inside the FCP X bundle because the database that drive Final Cut won’t be updated when you delete files manually. This could potentially cause all kinds of problems.

      You might look into Final Cut Library Manager, by Arctic Brightness, which does an EXCELLENT job of deleting render files and managing FCP X projects. This is a very inexpensive program that I use all the time.


  6. Marc Lamb says:

    Hi, Larry, I did as you suggested: Ran First Aid on Boot Disk in SafeMode, then created a new user to open FCPx. Still crashes when I Deleted Generated Event Files. Sigh.

    I’ve been “trashing files inside the FCP X” with no problems for over five years now. I don’t get it. But I’ll look into Artic Brightness. Thanks for the tip. 🙂

    • Marc Lamb says:

      FYI: I meant “trashing files inside the FCP X” via the Delete Generated Event Files option, not manually, as you rightly cautioned against.

  7. Marc Lamb says:

    Wow. That FCP File Manager by Artic Brightness is very cool! Can’t believed I’ve had to live without it for so long! Thanks so much for the heads up on this FCP add on.

    For anyone interested, here’s the link to it: https://www.arcticwhiteness.com/finalcutlibrarymanager/download/

    Basic program is free, then pay for extras as needed.

  8. Daniel says:

    I didn’t know until now that when I delete “unused” generated library files (when I’m editing in proxy) that it forces ALL of the Optimized Original version to have to render from scratch again. I really thought it was supposed to only delete “UNUSED” generated event files. A whole day of my life wasted rendering for absolutely no good reason.

  9. Diogo says:

    After deleting all generated library files, how do you copy the project to an external disk? I mean, the project file was 208gb and now is 8gb.

    Do I just copy the folder where everything is from my computer hard drive to my external hard drive or not really?

    Best Regards,

    • Larry says:


      Just copy the library file in the Finder from one place to another.

      However, if, when you import, you choose “Leave files in place,” you’ll also need to copy the media from wherever it is stored to the new location as well.


  10. Lorne says:

    There is a bug between Coremelt and FCPX
    Lock and load, slicex, etc.
    The watermark remains after correct licensing, and re-render ?

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