Managing Render Files

Posted on by Larry

[ This article was first published in the Feb/March, 2008, issue of
Larry’s Final Cut Pro Newsletter. Click here to subscribe. ]

One of the questions I get asked a lot is how to manage render files in Final Cut Pro.

The answer is that render files are easy to manage if you understand some key concepts.

NOTE: “render” has a simple definition, even though it has an unpleasant name. “To render” means “to calculate.” Complex effects need to be calculated before they can be played in real-time. It would have been easier for all of us if the programmers had just called them “calculated files,” but, no, they needed to intimidate us instead.

Here are the basic concepts behind render files:

  1. Render files are contained in the sequence, not the clip.
  2. There is a maximum of one render frame for every sequence frame
  3. Rendering a nested sequence does not affect the rendering of the clips contained in the original sequence.
  4. Changing an effect, transition, or clip visibility instantly deletes all the render frames associated with it. (Yes, they remain as part of the Undo queue, but, essentially, when you alter something that has render files associated with it, the old render files are gone.)

Render files are exactly the same size and format as your sequence settings — with one exception. With the release of Final Cut Studio 2, and the introduction of the ProRes 422 codec, Apple has added the capability of rendering HDV and XDCAM HD/EX video using ProRes, instead of the native format. Based on my tests and reading, I think this is a good idea.

Render 1

First, rendering is about 35% faster when using ProRes rather than the native codec. depending upon the speed of your computer and the complexity of your effect. Second, you are creating render files in a higher-quality format, which means that there is less image degradation during rendering.

Render 2

The only negative to this approach is that ProRes file sizes are four to five times bigger than the native codec. The reason for this is that ProRes is much less compressed than either HDV or XDCAM, which accounts for it’s increased speed and image quality.

When you change the visibility of a track, by toggling one of the green visibility lights, you automatically delete all render files associated with any clips on that track. This is because render files are tied to the sequence, not the clips. You’ve just changed the content of the sequence, which affects the render files.

Render 3

A much better approach is to make individual clips invisible by control-clicking a clip and unchecking Clip Enable. You will still lose the render files associated with that specific clip, but you won’t lose the render files for an entire track. (The keyboard shortcut to toggle Clip Enable is Control+B.)

During the course of editing a project you can essentially ignore managing your render files. Final Cut handles them automatically. Similar to the video you capture, render files are stored in your scratch disks, in a folder named after your current project, in either the Render Files folder or the Audio Render Files folder.

Render 4

When your project is complete, output, signed-off, and paid for, then, you’ll need to delete your render files to regain disk space. There’s never a reason to archive render files, as Final Cut will recalculate any missing render files. And, in fact, each version of Final Cut brings improvements in rendering, so there’s no good reason to retain render files from a project created by an earlier version of Final Cut, as the new version will make them look better anyway.

Unlike Media Manager, which should be avoided by any individual with common sense, the Render Manager works great. Even better, it’s easy to use.

Render 5

Choose Tools > Render Manager to display the window. Render files are separated as either video or audio renders, and stored first by sequence and then by project. Render files are grouped by sequence; within Render Manager you can’t see individual effects.

Render 6

To delete a render file, simply click in the delete column and click the OK button at the bottom of the window.

If the render file was created recently, you’ll get a warning saying that deleting render files will empty the Undo cache. In all cases, deleting render files is not undoable.


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9 Responses to Managing Render Files

  1. Austin says:

    Larry, This was the best explanation about managing render files I found. I’m still concerned about deleting them from the Render Manager when I have saved upwards of 50 versions of my project (with slight change in name) as a backup precaution–and not all of these saved versions are showing up in the render manager list. Now I am not sure that if I delete these earlier versions whether some complex rendered file that was in them might somehow unrender clips in the current version in a way that makes them unrenderable–for instance, a rendered file in a back-up program was the basis for a current render. This is my first attempt to delete render files, and only because I am getting a message pop up that says I am out of space for the renders or something like that, yet I have 60 gigs of Hard Drive space!


    • Larry Jordan says:


      Render files NEVER use other render files for rendering. Never.

      Render files always use source media files. As long as you don’t delete your source media, the worst that would happen if you delete too many render files is that FCP will re-render your missing elements from the source files on your hard disk.


  2. Mark Levinson says:

    I’m not sure if this is the right place for this, but I’m looking at any info on rendering that could help me understand why my render files seem to get lost when I leave a sequence I’ve rendered and return. I’m working with a Pro Res sequence, in unlimited mode. I render with Pro Res, the “orange” unlimited pieces. I save. And when I go to another sequence or project and return to the rendered sequence, the “orange” is back. Any suggestions would be greatly appreciated.

  3. Roger Klug says:

    Larry, Thank you for this enlightening article. is there a way within FCP to find where a project’s render files are stored? I have a bizarre situation which no tech has been able to solve: during a recent bulk render of AVIs and MP4s in a sequence, FCP was set to render to an external drive, but the files did not appear there in the default folder; instead, I saw the available space shrinking on my internal drive… not only that, the render files are nowhere to be found, not in Finder, not by several 3rd party apps, but FCP is referencing them! They show up in Render Manager in a folder, but are invisible to Finder. Any ideas?

  4. Jerominus says:


    while this is really very good help it seems limited up to FCP 7. I am in the midst of setting my system on FCP X and many terms/ concepts and menu items have disappeared – leaving us out there totally bold.

    One of the things I need to do is set scratch disk limits to my new external HD properly… but system settings seem to have disappeared from planet FCP?

    So what is happening with the scratch disk allowance?

    Many thanks for your good advice and well documented website!

  5. Simon says:

    Excellent training and Information. Thanks a lot.
    My question relates to FCPX and huge (360 GB) render files that have been created and are leaving me with very little space on my hard disk-approximately 160 GB and shrinking – I can’t even duplicate the project because the space is too small, now.
    I wonder if I can simply delete the render files in Final Cut’s Project Folder and let Final Cut 10 re-render the project. Will that make the render files total size smaller? I am assuming there are multiple redundant render files there – but I’m guessing here 🙂
    If this is not an optimal solution to the problem of huge render file creation what do you suggest I do to make smaller render files? Or is this unavoidable? The length of my project is about 40 minutes.
    Many thanks.

  6. Larry says:


    I normally delete my render files manually in Finder. When hard drives fill up, I look at the old projects that no longer matter to me and delete the render files from them. This system has worked well for me over the past several years. Is it better to use the Render Manager?

  7. adam v says:

    so is it safe to delete render files from a project folder and then re render? i am getting a quicktime error 50 when i export though i tried the first portion of my film and it worked….so not sure if thats a render file issue or something else….anyone know?

  8. Nick says:

    Hi Larry,

    When it comes to render files eating up so much space on my HD, I’m wondering if I’m editing from an external HD, if there is a way I can get those files to save on the external HD rather than my laptop’s HD. Thanks for the help.

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