Kibana - '?_g=' and '&_a=' Parameters in the Dashboards URL String

I'm struggling to find documentation on this, if I load up a dashboard their appears to be two query parameters we can add: '?_g=' and '&_a='

Currently I have a string like this on the end of my Kibana URL:

/app/dashboards#/view/Summary?_g=(filters:!(),refreshInterval:(pause:!t,value:0),time:(from:'2020-12-15T00:00:00.000Z',to:'2021-02-05T04:30:00.000Z'))&_a=(description:'',filters:!(('$state':(store:appState),meta:(alias:!n,disabled:!f,index:'dataset01*',key:case,negate:!f,params:(query:0001),type:phrase),query:(match_phrase:(case:0001)))),fullScreenMode:!f,options:(darkTheme:!f,hidePanelTitles:!f,useMargins:!t),query:(language:lucene,query:''),timeRestore:!f,title:Summary,viewMode:view)

When the dashboard loads like this is displays a time range and applies a filter of case='0001'.(keyword field) This works but I'm looking for clarification on a few things.

  1. The difference between '?_g=' and '&_a=' ?
  2. Any documentation on creating these strings?
  3. Way to shorten link? The link is pretty ugly to send around or display in a visualization. I would like a way to shorten it by only passing in the case=0001 query and nothing else, can this be passed in as a simple filter and not the long meta string.

I had looked at using the Kibana shorten URL API, but thought it would work better if instead of assigning me a random ID, it assigned me something I could choose.

The data in the URL parameters is the application state that has been encoded in "Rison" format. The _a parameter is "app state" and the _g parameter is "global state", which is state that moves between apps with you (such as pinned filters).

You can use a tool such as the following to make sense of the data:

Keep in mind that the format for URLs is likely to change in future Kibana versions.