You're halfway through a masterpiece. The color grading is set, the transitions are crisp, and you go to hit export. Then, that little grey box pops up: iMovie must complete other tasks before performing this operation. It’s annoying. Actually, it’s infuriating because iMovie doesn't tell you what those tasks are or how long they’ll take. You’re just stuck staring at a progress bar that isn’t moving.
Most people assume their Mac is broken. It isn't. Usually, this error is just iMovie’s way of saying it’s overwhelmed. It’s juggling background rendering, analyzing clips for stabilization, or trying to sync with iCloud all at the same time. If you try to force an export or a heavy edit while these gears are still turning, the software simply gives up.
Why Does This Error Actually Happen?
Basically, iMovie is a background-heavy app. Unlike professional suites like Final Cut Pro where you have a bit more transparency, iMovie hides its "thinking." When you drop a 4K clip into the timeline, iMovie immediately starts generating render files so you can playback the video smoothly. If you try to share that movie while it's still generating those files, you get the "must complete other tasks" alert.
Sometimes, the culprit is the iMovie Theater or iCloud sync. If your preferences are set to automatically upload everything to the cloud, iMovie might be struggling with a slow upload in the background. It won't let you start a new heavy task (like exporting a 1080p file) until the upload handshake is finished.
Another weird one? Analyzing for rolling shutter or stabilization. If you’ve clicked those boxes in the adjustment bar, iMovie has to frame-by-frame analyze your footage. It’s a CPU hog. If you have an older MacBook Air with limited RAM, this process can take ages, and the "tasks" iMovie refers to are simply these invisible calculations.
How to Kill the "Other Tasks" Loop
First, stop clicking. Seriously. Every time you click "Share" again, you’re potentially adding to the queue. Look at the top right corner of the iMovie interface. Do you see a small, spinning circle? That’s the activity indicator. If that circle is there, iMovie is busy. Hover your mouse over it. Often, a tiny tooltip will appear telling you exactly what it's doing, like "Rendering" or "Importing."
Give it five minutes. I know that sounds like "have you tried turning it off and on again" advice, but for iMovie, it’s often the only fix. Walk away. Get a coffee. Let the background processes finish. If the circle disappears and you still get the error, then we have a deeper data glitch.
The Power Cycle and Cache Clear
If waiting doesn't work, you need to clear the mental fog. Close iMovie. If it won't close, use Command + Option + Escape to force quit it.
Now, try this: hold down Command and Option while you click to open iMovie. A dialogue box will pop up asking if you want to delete preferences. Say yes. This sounds scary, but it doesn't delete your projects or your media. It just resets the app’s internal settings to factory defaults. This often "un sticks" whatever phantom task was hanging in the background.
When Background Rendering Goes Wrong
Sometimes the render files themselves are corrupted. This is a classic iMovie headache. You might have a "dead" frame in your timeline—a tiny sliver of a clip that iMovie can't figure out how to process.
Go to the iMovie menu at the top of your screen, select Settings, and look for the Render Files section. There’s a button that says Delete. Hit it. Don't worry, iMovie will just recreate these files as you edit. By deleting them, you’re forcing the software to start fresh. Often, the "must complete other tasks" error disappears immediately because the "task" it was struggling with—processing a broken render file—no longer exists.
Handling Large Libraries and Storage Issues
Is your hard drive almost full? This is a huge factor. iMovie needs "scratch space" to work. If you have 5GB left on your SSD and you’re trying to export a 4GB movie, iMovie will choke. It might report this as "completing other tasks" because it's effectively trying to move data around to find a home for your new file and failing.
Ideally, you want at least 15-20% of your total storage space free. If you’re editing off an external drive, make sure the drive is formatted as APFS or Mac OS Extended (Journaled). If you’re using an old drive formatted as ExFAT or NTFS (via third-party drivers), iMovie’s background database management will constantly trip over itself, leading to that "other tasks" warning.
The iCloud and Photo Library Connection
If you are pulling clips directly from the Photos app within iMovie, you're adding a layer of complexity. iMovie has to "request" the full-resolution file from the Photos library. If that file is stored in iCloud and hasn't been downloaded to your Mac yet, iMovie has to wait for the download to finish.
The "other task" in this scenario is literally a background download from Apple’s servers.
To avoid this, I always recommend dragging your clips out of Photos and onto your desktop first. Then, import them into iMovie from the desktop. It’s an extra step, but it severs the link to the cloud and makes the files local. Local files don't require background "tasks" to fetch data.
Step-by-Step Troubleshooting Checklist
- Check the Circle: Look at the top right. If it's spinning, wait. Hover for details.
- The "Wait and See": Give it 10 minutes of total idle time.
- Reset Preferences: Hold Command + Option while launching the app.
- Delete Render Files: Go to iMovie > Settings > Delete Render Files.
- Check Disk Space: Ensure you aren't redlining your storage.
- Force a Re-index: Sometimes moving the project to a new Library (File > New Library) can reset the background task queue.
Nuance: Hardware Limits in 2026
If you're running iMovie on an older Intel-based Mac with 8GB of RAM, you're going to see this error more often than someone on an M2 or M3 chip. Silicon Macs handle unified memory much better, meaning they can "multitask" within the app without locking up. If you are on an older machine, the best thing you can do is close every other app. Close Chrome. Close Spotify. Give iMovie every ounce of RAM you have.
Sometimes the "task" it's completing isn't even in iMovie—it's the MacOS trying to swap memory because you have 40 tabs open in the background.
Actionable Next Steps
If you are looking at that error message right now, don't keep clicking "OK." It won't help. Instead, follow this specific sequence:
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- Force Quit: Hit Command+Option+Esc and kill iMovie.
- Reboot: Restart your Mac. It sounds cliché, but it flushes the system cache.
- Open with Option/Command: Reset those preferences.
- The "Slow Export" trick: Instead of clicking the Share icon, go to the File menu > Share > File. Sometimes the top-level icon triggers a different background check than the menu-level command.
- Check for Updates: Open the App Store and ensure you’re on the latest version of iMovie. Apple frequently pushes small patches that address "hangs" and background task errors that aren't explicitly mentioned in the patch notes.
By clearing the render files and resetting the preferences, you're essentially giving the software a clean slate. Most of the time, the error is just a ghost in the machine—a task that finished long ago but didn't properly "check out" of the system's memory. Clear the fog, and you'll be back to your export in no time.