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  • Troubleshooting

The disk is full and an app will not let you save. What to do in the next minute

A save that fails on a full disk risks the document. The fastest safe space, and how to get the file out before anything else.

5 min read

This is the urgent version of a full disk: you have unsaved work in front of you and the application has just refused to write it. The order matters here, and it is not the order in most cleanup advice.

First, protect the document

  1. Do not quit the application. Unsaved work lives in memory and quitting is what loses it.
  2. Try Save As to a connected external drive or a USB stick, which sidesteps the full disk entirely.
  3. If there is no external drive, select all and copy the content into a message or note that syncs elsewhere.
  4. Only then start freeing space.

Applications with autosave usually have a recovery copy, but a recovery copy also needs disk space to write, which is precisely what is missing. Getting the content off the machine is more reliable than trusting recovery in this specific situation.

The fastest gigabytes, in order

df -h /System/Volumes/Data
ls -lhS ~/Downloads | head -10
tmutil listlocalsnapshots /
  • Empty the Trash. Instant, and often several gigabytes.
  • The largest file in Downloads. No deliberation, it is an installer.
  • Local snapshots. sudo tmutil thinlocalsnapshots / 5000000000 4 asks for roughly 5 GB back.
  • A device backup or virtual machine. The largest single items on most Macs.

Why the disk filled while you were working

Often it did not. Applications that edit large files write a temporary copy while saving, so a save can need twice the size of the document as free space. Video editors, image editors and database tools all do this, and it is why the failure appears at save time rather than gradually.

A scratch disk is the same mechanism with a different name, which is why Photoshop can fill a disk mid session and release it all when the app quits.

Once the document is safe

Restart the Mac. That clears swap and temporary files and gives you an honest picture, and then the order to free 100 GB is the unhurried version of this page. If the disk fills again within days, why a Mac fills up so fast covers what is growing.

Common questions

What do I do when a Mac says the disk is full while saving?

Do not quit the app. Try Save As to an external drive, or copy the content somewhere that syncs, then free space. Quitting is what loses unsaved work.

Why did saving fail when I had some free space left?

Because applications write a temporary copy while saving, so a save can need roughly twice the document size in free space. Large media and database files hit this well before the disk shows zero.

What is the fastest way to free space urgently?

Empty the Trash, delete the largest installer in Downloads, and thin local snapshots with tmutil. Those three take a minute and usually give several gigabytes.

Will restarting help when the disk is full?

It clears swap and temporary files, which frees some space and gives an accurate picture of what is really used. Do it after the document is safe, not before.

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