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.