My Mac "startup disk is almost full"

I am not sure where to look to find what this disk contains and why it's almost full.

See attached error...

Mac Startup Disk is Almost Full
I have a 500GB SSD and have worried for months it was almost maxed out.

How can I find what files can be deleted for this startup disk not to max out?
newbiewebSr. Software EngineerAsked:
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Have you emptied the trash? The OS does not free up space from trashed files until the trash is emptied.
newbiewebSr. Software EngineerAuthor Commented:
yes. It's empty.

When I delete a program that I no longer use, it is enough to simply delete it from Finder > Applications?

Or, like Windows, must I track down where that program was installed and blow away the folder?
I'd hop in and check out storage.  Under manage storage where is all your storage being used?  

do you have multiple drives?

Do you have a large amount of photo?  

Are you a heavy music listener that uses Itunes to backup their library on that PC?
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The first thing to do is to check out your downloads folder. Delete everything you don't need, particularly old installers.

Other then that, music and movies take up a lot of space. Then pictures, particularly if you save as RAW rather than JPEG.
newbiewebSr. Software EngineerAuthor Commented:
I followed your advice and emptied by Downloads, then Trash.

I do have many images, sadly, little music.

Images I am sad about since I have many many duplicates. I copy them in to various folders when I make a presentation. So, there are many images copies a handful of time.

Is there a solution to this short of redesigning my approach??
David FavorLinux/LXD/WordPress/Hosting SavantCommented:
Lot's of places to check.

Big one is Trash for all users, especially if some user's rarely login.

You can always check disk space usage via Applications -> Utilities -> Terminal -> df - which will show you % disk use.

This way you can tell the effect you're having, when you remove files.
Instead of making copies of pictures, use aliases:
newbiewebSr. Software EngineerAuthor Commented:
Thanks for the picture idea. That would save lots of room.

I have another related question here...

And thanks David for talking about "other users." I have Guest, but never use it and would like to remove it.

How much might that save? And how do I delete that user?

Also, "df:"revealed the following...

Download and run CCleaner and clean the data. This can make a big difference:

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newbiewebSr. Software EngineerAuthor Commented:
Be careful with ccleaner.  They were hacked in the past and malware put into their program.
newbiewebSr. Software EngineerAuthor Commented:

Any good alternatives?
ScriptAddict, be careful cholera killed 2/3 of the world population in the past.
The last ccleaner hack was mid September of this year.  When was the outbreak you mentioned?  

Read up on it.  

Nothing will get everything.  As our defensive friend  is attempting to point out they will likely be extra careful for a bit.  

The best thing to do is to keep your important data on the cloud and reset your Computer to factory once a year.  Think of it as an oil change for your computer.  And you will spend less of your life troubleshooting obscure problems.
Ccleaner has over 6000 updates. Oly once there was an issue with the 32bit free version for Windows, and the problem appears for those who had the update installed on the PC.
Glad you got your Mac working better again.  Merry Christmas!
David FavorLinux/LXD/WordPress/Hosting SavantCommented:
Yep. I'd think twice about cc-cleaner.

If you have many duplicate files, try DupeGuru running one pass for exact matches + a second pass for fuzzy matches (if you have many photos).
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