Does Dropbox sync incremental updates to files or the whole file each time?

Question

We use Dropbox to store and sync quite a few large files between multiple machines and users.

What we where wandering is if you have a 100MB file and it gets uploaded once, (and downloaded to all other machines once) then you make a change to that file, Dropbox will now try to re sync that file, is it re syncing the whole file or can it work out the changes and just sync them?

I.e. does it sync 100MB each time or just the changes, say circa a couple of mb?

I know that they used to sync the whole file each time, but the post I found (on an external blog) saying that was 2 years old, and I wandered if anything has changed since.

Answer 1

Dropbox does incremental sync.

Official Statement:

Before transferring a file, we compare the new file to the previous version and only send the piece of the file that changed. This is called a "binary diff" and works on any file type.

Source.

Answer 2

As far I know Dropbox is able to differentiate between new and old version file types and does an incremental update of the same

Answer 3

In my experience Dropbox does NOT incrementally update a file: I have a 8 GB text file (Gmail backup via Takeout) slightly updated and it is re-uploading the whole file lasting hours.

Things can't be any better with binary files I guess.