Over the years I collected hundreds and hundreds of website bookmarks. This morning I cleaned up my old bookmarks.
Many of the links were dead.
Many of the bookmarks were duplicated. Backups of backups and copies of copies either intentional or accidental.
I went through them all. Deleted the dead links and duplicates. In the end, I had 66 bookmarks that were worth keeping if only to look at one more time.
There is no automated way to do this. You need to bite the bullet and just reviewing thing manually. It will take a bit of time and effort and it will be worth it.
Don't keep outdated data.