If you have many cards on a board, it may be sensible to reduce card size to allow for a better overview.

In order to change card size, go to board settings (the three dots next to the board title), scroll down and enable "Hide card description" (see image below).

The smaller cards will be in the same format, but they will only show the title (unless you open it).

Card size is controlled at the board level and can easily be reversed by disabling "Hide card description".
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