I have a warning on my Mac stating 'your computer is low on memory'...close applications to free up memory...how to do that

Either your storage is low on free space, and macOS cannot create new swapfiles. For most people this is Not the case.

A running process (or processes) are asking for an excessive amount of virtual memory address space. The manage virtual memory the macOS kernel needs to create page tables. If enough virtual address space is requested, the macOS kernel has so much RAM tied up in page tables, there is no longer room for applications.

Applications -> Utilities -> Activity Monitor -> Memory may help you identify apps that are using a lot of RAM.

As someone above has mentioned, a web browser that has lots of tabs open can consume a lot of memory. The problem is that web browsers tend to create a separate subprocess for each tab, so no single process in Activity Monitor will look like it using a lot of memory, but in total the web browser may be going crazy.

It could be another app (or set of apps) such as video or very large image processing.

How much memory do you have? Close all your applications; restart; and see where things stand when you begin to restart applications. Be sure and don't have an excessive number of browser tabs open.

Try rebooting.

EtreCheck is a simple little app to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac.

http://www.etresoft.com/etrecheck

Pastebin is a good place to paste the whole report...

https://pastebin.com/

Or use the paperclip at the bottom of a Reply to attach the full report here. :)

Do you have a lot of Safari tabs/windows open at the same time?

What model of Mac is this and what version of macOS and how much memory does your system have?

Perhaps an etrecheck report might give some clues?

Good luck...

what can I do if on my computer is a warning "your computer is low on memory"to free up some memory close a few applications" and I can do nothing and can't work on my computer

what can I do??