What Is a Long Running Script?

A long-running script is a JavaScript or ActiveX code that causes Web browsers to display the long-running error message. Also known as the runaway script dialog, this message indicates that the browser is taking a long time to execute a script.

A long-running script often causes performance issues and makes the Web page unresponsive. It forces long-running error messages to appear, because every Web browser has a specific timeout for script execution. Users may opt to let the script continue running, but they can also choose to terminate the script, especially when it's running an endless loop. Users can prevent the error message from showing again by disabling script error notifications in the browser settings.