Running out of disk space / no space left (Mac OS)

One of ways to find out what's eating up space on your Mac is to download a third-party program that can analyze and break down what's using the most space. One such tool is the Disk Diag tool. This tool will show you what's using most of your space and how much space, allowing you to make informed decisions.

Freeing up disk space is removing data you don't need. Some of that data is visible and accessible to you (photos, videos, music, games, and other documents), however, some of the data you have isn't (e.g. cached data, and temp files). Locating the hidden data is time consuming and dangerous, because if you remove something you are not allowed to, you can cripple the operating system.

There are many free third-party software solutions that will help you clean your computer, with some of them being CCleaner and iObit. Install a software solution of your choice, run a scan, and it will inform you what can be safely removed. After your confirmation, data will be removed.

If you have photos, music, videos, or other files that you want to keep but don't necessarily want on your device, consider saving them to removable media (offline storage), such as an external drive, USB drive, DVD, or cloud (online) storage, such as Google Drive, iCloud or Dropbox.

You'll still be able to view those files, and copy them back to your device, as long as your devices connected to the removable media or cloud storage, but they won't take up space on your device.

Note: Feel free to check out the solutions on how to back up your data.

Majority of computers allow for upgrading the storage capacity, thus freeing up more space. All you need to do is to go to take your computer with you to a store, purchase a storage drive, and have it installed by professionals.

If you use Apple's Mail app or another third party app, your Mac is saving email attachments and message archives unless you've told it not to, or route attachments elsewhere, like Google Drive, OneDrive, Dropbox, and others.

Pay attention how much data is stored in your Mail.app, and clean it regularly to free up space.

Computers run faster when there is more free space available on the hard drive.

Therefore make it a habit to  do a clean up to free up space which will make your computer faster. 

For example, a "quick win" is to delete files by moving them to the Trash: drag and drop a file on the trash icon in the dock, control-click on a file and select Move to Trash from the menu, select a file or files and use the keyboard shortcut: command-backspace or select a file or files and click File -> Move to Trash from the menu bar.

To empty the Trash, control-click or click and hold on the trash icon in the dock and choose Empty Trash from the menu that appears, or from the menu bar use the keyboard shortcut command-shift-backspace. 

Also, running frequent scans with CCleaner, MacBooster, or other similar software is advisable so that you clean the cache, temp and junk files, which also occupy disk space.