Keeps the values of a successful fetch for this many MINUTES: all pages, after the expressions, the filter and the order. The build form, the check of a submitted value and Rebuild use them instead of contacting the endpoint again, whatever caching headers the endpoint sends. If the value is set to 0, nothing is kept and every request contacts the endpoint.
A submitted value that is not among the cached values is checked against a new fetch, so newly published values are accepted. Failed fetches are not cached.
The refresh button next to the parameter on the build form fetches the values again, bypassing the cache, and administrators can clear all cached values in the global Jenkins settings. Changing this parameter's value source (endpoint, credentials, expressions, filter, order, headers or pagination) also stops earlier values from being used.
NOTE: Below this cache, endpoint responses are also kept in an HTTP response cache on disk (50 MiB per default, adjustable in the global Jenkins settings) as long as the endpoint's caching headers allow it.