For bookmarklets there are no prerequisites.

For userscripts the browser needs to install a plugin a userscript manager like Grease Monkey or Tampermonkey that build  must be installed to the browser. The userscript manager builds the context in which the script is executed.

The userscript can be configured to be automatically executed on every page whose URL matches a regular expression. This way a user may select the script to remove element only on certain spaces, while leave them untouched on others.

A userscript is a JavaScript script with some metadata. It may also use services provided by the userscript manager context.

The following screenshot shows the script installed with Tampermonkey.

You may want to edit the script and adjust the match URL to your Confluence server.

// @match        https://*/confluence/*

The browser plugin may also take care of automatically update the scripts. The source of the script could be hosted in a controlled environment. We recommend to copy the script to your server and alter it to meet your specific requirements.