Quicksilver is a unified, extensible interface for working with applications, contacts, music, and other data. When opened, it will create a catalog of applications and some frequently used folders and documents. Activate it, and you can search for and open anything in its catalog instantly. The search is adaptive, so Quicksilver will recognize which items you are searching for based on previous experience. It also supports abbreviations, so you can type entire words, or just fragments of each. When not in use, Quicksilver vanishes, waiting for the next time you summon it.

Quicksilver’s greatest strength, however, is not search. Any item you are able to find, drag, or otherwise pull into its universe is endowed with many potential uses. Hitting <tab> takes you to the action field, where you can use the same adaptive search to select what you would like to do. Among other things, files can be emailed, copied, compressed. Text can be modified, transmitted between programs, or searched for on the web. Some actions even support an indirect object, so you can send an item to a person, move files to another folder, or open files with a specific application.

Quicksilver can be given the ability to understand the data inside of files, allowing you to work with data in new, faster ways. Plug-ins add both new items and new actions, allowing you to run scripts, send instant messages, dial phone numbers, look up words in a dictionary, queue up songs in iTunes party shuffle, and much, much more. Frequently used commands can be bound to triggers, giving you the ability to execute them immediately by hitting a hot key or using the mouse on a corner or edge of the screen.