On Windows, Dropbox has a global file watch and does filtering to determine if the files should be synced: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=9136546" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=9136546</a>