ScriptRunner’s built-in scripts are automated functionality for a Confluence administrator. Each built-in script does a certain job which typically converts a manual process to a largely automatic operation. The ones found in ScriptRunner for Confluence Cloud are all one-off functionalities that an administrator (or space admin) can use to save massive amounts of time when organizing.
Confluence has a lot of ways to differentiate and attach information to a page, but sometimes people make mistakes, add too much, or the processes change. Since admins have a lot to keep track of and manually deleting or changing items one a time is tedious, it is easy to miss something. The automation provided by built-in scripts can prevent that. For example, label systems can be ruined by misspellings or unconfident hyphens, but you can use the Rename Labels script to rename labels in bulk.
The number of available built-in scripts you have depends on what version of ScriptRunner for Confluence Cloud you are running. Please visit the Developer Documentation for more information.
There are two sets of built-in scripts for different administrators: