Every monitor runs some standard checks, which depend on the monitor type. Additionally, in the error conditions of a monitor you can define custom checks to generate alerts for specific situations. The knowledge base article Error conditions explains what they are and how to use them.
This article explains how the error conditions of the category Size work. In a monitor you can find them on the tab Error conditions in the section Size. To activate the check, tick the check box in front and fill in a value. Note that not all monitors have all error conditions. Check the table in Which error conditions are available? to find out which options are available in certain monitor types.
Total minimum bytes
The lower limit of bytes to get back in the server response. If the size of all page elements combined is below this number, this could indicate that your page is missing content and may not function correctly.
Total maximum bytes
The upper limit of bytes to get back in the server response. If the size of all page elements combined is above this number, there is too much content. This could be a mistake in your content or a hint that content was placed on your website without your intention and consent.
Element maximum size
In addition to checking the total page size, you can also run a check on individual element sizes. Fill in the maximum expected size here to receive alerts when any element on the page exceeds this size.
Ignore external elements
Enable this option to exclude all external elements from the size-related checks mentioned above. Please note that enabling this option does not mean that external elements are not downloaded during the execution of your monitor. They will still be downloaded to not disrupt the correct execution of your page. As a result, the waterfall chart will still show those external elements. If you do want to block specific requests for external elements (third party elements) completely, please use the blocking options on the Advanced tab of the monitor settings.