Pruning Assets

I am concerned about the amount of assets I have with a website.
I'm reuploading a website (deleted the existing files on the server and republishing the site).
But I uploading a lot of unecessary stuff.

Over time, assets get changed, modified, copied and reused in other parts of my websites
and many get replaced or deleted from the site.

However the assets folder...and other page elements in other folders... are excessive.
I've got multiple duplicates, redundant items, removed items, etc

Is there an easy way to remove everything that is not currently being used on the website?
In my case the site is too big, the files too many, to go through manually and delete things.
I'm also not sure, looking at the items in the folders, exactly which things I can delete and which I cannot, especially when it comes to duplicated things.

I thought there might be something built in that can compare the existing website template to whats being saved.