Adobe Illustrator when working with large files

@Edward384 for me, if I noticed a lag on my computer, I would close any application that I am not using such as Photoshop 2024. For me, with the AI technology, I noticed my computer is working hard when the fan turns on my MacBook. Once, I close that off, the fan slowly turns down. 

Not joking but a former student once had over a hundred icons on her desktop, and while trying to download a file from Adobe, I noticed that she also had over 100 web broswer tabs open too. Each open application, file, and we browser tab uses a portion of your computer's RAM. Too many of them can overwhelm your system's memory, leading to slowdowns and even crashes...I did tell the student to move those files from the desktop and close the tabs. Once she did, her Adobe Illustrator was able to work properly. 

Another thing...your recylce bin/trash can isn't a place to store your files; that's to be deleted. Delete unnecessary files, empty the recycle bin/trash can, and run disk cleanup to free up space. You be amazed how many people keep files there and never delete them. My brother-in-law does this...I accidentally emptied his trash because he said his computer was slow...oops! But now, the computer is faster than before! 

Is the file simply large in file size or are you working with a document that has a really large art board size? If you are working on a project such as a vehicle wrap, a billboard ad, a sign or other large format layout and designing it at full size make sure the document raster effects settings level is not set at a default such as 300ppi. That would be overkill and could put a serious strain on the computer depending on what kinds of effects were being applied. For example, it's common for billboard faces to be designed at a scale, such as 1" = 1'. A 300ppi setting isn't too bad for that, even for a 48' X 14' board; the design is 48" X 14" (not counting bleed). Blown up to full size the ppi level drops to 25ppi. That sounds coarse, but viewing distances are pretty far.

in the future, to find the best place to post your message, use the list here, https://community.adobe.com/

p.s. i don't think the adobe website, and forums in particular, are easy to navigate, so don't spend a lot of time searching that forum list. do your best and we'll move the post (like this one has already been moved) if it helps you get responses.

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What problem are you dealing with in detail? What is making the file large? Effects? Too many anchor points? You might be able to simplify a path or create a graphic style that can be applied. Need more info to really help.