I have a big issue with the storage on my Macbook Air. The "Other" category is taking up 65GB! That's more than the system, documents, pictures etc all together! I already deleted junk, old files and even safari history + caches. How do I delete this

Here's another reliable way to check. Download and run Etrecheck  It is a lightweight diagnostic tool that will create a snapshot of your system. It will contain no personal information.

To post the log file click on share report and use the Page icon in your reply window.

The Storage tab is known to report incorrectly. Also check by choosing your Mac HD and "Get Info" (command-i). It may be different. Try rebuilding Spotlight index.

How to rebuild the Spotlight index on your Mac - Apple Support

Some of the space may also be from Time Machine Snapshots.

About Time Machine local snapshots - Apple Support

After you've freed up some space download Omni DiskSweeper:

https://www.omnigroup.com/more

DiskSweeper can give you a more accurate read of disk space than Finder or Storage Tab of About this Mac. It can also show you the precise size and location of all your files. It will inventory your disk starting from the files that take up the most space. If you want you can even delete files from OmniDisk Sweeper. But be careful some of the items may be important to your system.

It's odd that DiskSweeper would be wrong, I've never seen it in error. Choose your Mac HD and "Get Info"(command-i), how much free space is that reporting?

Other is made up of various stuff, some yours so don't just try to delete it. See this Support Topic, if in fact you need to make space:

How to free up storage space on your Mac - Apple Support

Etrecheck seems to be in line with what you your Mac is telling you. You should uninstall BitDefender though, as per the developer's instructions. It can conflict with Mac's own built-in security.

I can't explain what DiskSweeper is telling you.

This is what EtreCheck shows...

PP1999 wrote:

If I rebuild Spotlight Index, which folders should I select to be in the index before removing it again?

It shouldn't matter.

Glad to hear that.

Lucky you! I have 207 BB of "Other" and only 24 GB 'available' - no idea what it is or where!

I've no games and OmniDiskSweeper tells me my entire disk is only 36.0 GB! Mystery!

I'm not sure that DiskSweeper IS wrong! 'Get Info' claims 232.72 GB, but when I do 'Get Info' on all the folders they don't add up to anything like that and come closer to the DiskSweeper figure!

Okay, thanks, I'll do that...