SSD keeps filling up while running for no reason.

[Rydawg96]

I have a huge problem. For some strange reason, when my Mac boots up, my boot drive always has a few gigabytes free, but then after a few hours it fills up and and im left with anywhere from 500MB-2GB free, and this causes all sorts of problems when this happens from Mail quitting due to not enough storage to Time Machine failing to backup. And the real strange thing is, every time I reboot the storage becomes free again and all apps run normally...until the drive eventually fills up again for no reason and I have to keep rebooting to stop the problem every time in occurs. How is this even happening? What app could possibly fill up my main drive like this?

 

[gilby101]

For some strange reason, when my Mac boots up, my boot drive always has a few gigabytes free, but then after a few hours it fills up and and im left with anywhere from 500MB-2GB free, and this causes all sorts of problems

Ouch! A "few" GB free is a worry. I am not surprised you run into problems. For performance and SSD lifetime you need 20% free. Is this a tiny 256GB SSD?

What app could possibly fill up my main drive like this?

You are going to have to investigate. I use DaisyDisk to analyse how disk space is being used.

 

[AnonMac50]

Virtual memory. In other words to put it simply, RAM usage sometimes spills over to the SSD (for example when there isn't enough RAM left). For example, if you have many tabs in a browser, you might regain some storage space when you close the app. When you reboot the machine the RAM clears up and the computer runs fine until it runs out of RAM and starts using virtual memory. See if you can clear any space up from your computer. I like to use "GrandPerspective" to check.

 

[nmt1900]

When amount of free space is less than 20%, it will be serious hit on any SSD performance - just as with mechanical HDD storage as there will not be enough free space to optimize storage. For SSD it will affect the lifetime as well as free space is used to wear leveling. If we are under 5% then any system will start having problems.

 

[fivenotrump]

I have had this happen twice (on only one of my Macs, a MBA M3) since updating to 15.4.1.
This Mac normally has 140-150 GB free.
On both occasions I noticed that TM backup had failed and that free space was almost zero.
Was not running anything unusual. Reboot fixed it.
I hope to catch it sooner next time in order to investigate.

 

[rmrcu]

I have a huge problem. For some strange reason, when my Mac boots up, my boot drive always has a few gigabytes free, but then after a few hours it fills up and and im left with anywhere from 500MB-2GB free, and this causes all sorts of problems when this happens from Mail quitting due to not enough storage to Time Machine failing to backup. And the real strange thing is, every time I reboot the storage becomes free again and all apps run normally...until the drive eventually fills up again for no reason and I have to keep rebooting to stop the problem every time in occurs. How is this even happening? What app could possibly fill up my main drive like this?

If I read this correctly, you have a 1TB ssd but your boot drive only has a few gigabytes free. It sounds to me like you should increase the size of your boot drive--since you have only 8GB of ram, the os needs disk space to do swapping and cacheing.

 

[KenSM]

Try offloading some of the files on your internal SSD to an external one. My M1 Studio has a 1TB drive, and if I loaded all the photographs I take onto it, it would soon be full – so I write all my photograph files initially to an external SSD, and only write a selection of these image files to the internal storage. I have a number of Samsung T7 2TB drives, though of course other brands are available, as they say. Although the read/write speeds of my internal drive are much faster than the external drives, in practice when I access image files from the external storage I see no difference in the time it takes to load them.

 

[NiwPix]

I had this exact same issue recently and solved it.
Macbook Pro M1, 1 TB SSD, 16GB Ram
I was hovering around 800GB until recently I got a notification my SSD was full ( like less than a GB remaining ). I deleted a large game, 100GB...and within a day my SSD was full again. I restarted the laptop, deleted small video, cleared browser cache...did some sudo stuff that ChatGPT suggested. All to no avail.
The culprit: I had a pending MacOS update...15.5
I did that and now for several days my storage is normal, slightly above 800GB