Text-Diff.com was unavailable during July 16 to July 21 because of late payments with the server host. The bill has been paid and the server is up and running! Sorry for the inconvenience.
Meanwhile, I'm working on some improvements. One of the features is faster diffs by allowing to opt-in for processing on the server side. What else would you like to see? Drop me a feedback via text-diff.com (there is a feedback button n the bottom right corner!)
Thanks for using text-diff.com!