I had written a review that perhaps wasn't fair and I apologize to the developer. I deleted the old one. This is a new review.

Regarding the scan locking up, I think if you have a lot of duplicate bookmarks, what you need to do is start by dealing with those before you have it look for dead links. Once I did that, it went much more quickly when looking for the dead links and it did complete the scan. This extension also worked to fix redirects and stuff. You have to look over each one because it did find some false positives, which is natural and I think it even said to be careful in the dialogue itself. Can't remember for sure, but just don't blindly click your way through this stuff.

I don't know how I had so many duplicates, but it would have been nice to have had a way to select them in bulk.