Convert Linux file permissions between different formats.
Look for the non-existing command name to find and install the appropriate package from each Linux distro.
Generate crontab syntax for your cron jobs.
Check DNS records against a selected list of DNS servers located in multiple regions worldwide.
DNS speed benchmark
Test the performance of the DNS servers of a domain name from all over the world.
Check the functioning of the rewriting rules of your htaccess file.
mess with dns
Learn DNS by setting up DNS records.
Free website tracking service to check if they are online or down.