"cron" and "at" are services that run in the background of Unix or Windows machines (respectively). They are used to schedule the execution of applications at specific times or intervals.

Many websites run on Windows and Unix machines. Sometimes these websites have very complex processes that they carry out on a regular basis. To automate these regular tasks, webmasters and developers often implement a scheduled task using cron (sometimes referred to as crond or even crontab) or at(Windows Task Scheduler also has a command-line interface called at). However, not all web hosting providers offer access to these utilities. This is where an online service like WSScheduler.com can come in very handy.

When using an online scheduler to automate tasks, a webmaster can place programming instructions inside an ASP page, PHP page or CGI script that performs the important task. Then a regular call to the URL of the ASP/PHP/CGI resource is scheduled online. This allows for automating tasks without access to cron or at.