A webcron solution can be contained entirely on a web host by letting visitors trigger a webcron scheduler script on the server. For Thisinstance, isthis typically{{really?|date=Decembercan 2010}}be accomplished by using an [[img (HTML element)|'img' HTML element]] in the header or footer of the website., an [[ajax]] call in a script or an [[iframe]]. When a visitor views the website, the image loads, which triggers the webcron scheduler. The webcron scheduler runs any tasks that need to run and then outputs an image so the visitor's web browser does not display a broken image on the page.<ref name="phpJobSched" />{{psc|date=December 2010}} It may alternatively start the task [[asynchronously|Non-blocking_algorithm]] such that the [[http]] response is not delayed.
While the task runs, the visitor's web browser will wait until the server responds. Users of visitor based webcron scheduling typically{{really?|date=December 2010}} author scripts in a way so that the script does not execute for too long.{{citation needed|date=December 2010}}
If there are insufficient visitors to a website using visitor based webcron scheduling, then scheduled tasks will not run on time.
Since visitor based webcron scheduling enables the possibility of self-contained webcron solutions, it increases the portability of a website or web-based software product.{{citationneeded|date=December2010}} Many{{which?|date=December 2010}}Some web-based [[open-source software]] products that have tasks that need to run regularly typically{{really?|date=December 2010}} use a visitor based webcron solution to execute those tasks.{{citation needed|date=December 2010}}
