I've used online diff checkers in the past for their convenience, but in the end I went out of my way to find a convenient way to quickly diff two texts locally

I've used online diff checkers in the past for their convenience, but in the end I went out of my way to find a convenient way to quickly diff two texts locally. It's not that I believe that online diff checkers upload the contents to some third parties - in fact this one explicitly says everything is performed locally - but the fact that they _could_ made me feel uneasy.