Card keys

Every card has a short key such as PAY-12. Say it in a meeting, type it into search, or write it in a comment or a commit to point at the card.

In short

Every card has a short key: the board's short name, a dash and the card's number, such as PAY-12. Type it into search to jump to the card, write it in a comment to link the card, or put it in a commit to connect code to the card.

Before you start

Who: anyone who can open the board reads and uses keys. Changing the key needs "Create and manage boards".
Plan: every plan.
First: nothing. A board gets its key when it is made.

Steps

Copy the key from the top of the open card.
Type it into "Search" anywhere (Ctrl+K, or ⌘K on a Mac) to jump to the card, or into the board's own search.
Write it in a comment or description; it becomes a link for everyone who can open that card.

Open Board settings, go to "About this board" and find "What its cards are called". Only people who manage the board can change it.
Type a new key: 2 to 8 capital letters and digits, starting with a letter.
Press "Save key".

Result: every card on the board shows the new key, and keys written with the earlier key still open the same cards.

Good to know

A new board gets its key from its name. The key is the first letters of each word (Payments platform becomes PP), or the first three letters of a one-word name (Payments becomes PAY). If another board in the workspace already has that key, a number is added (PAY2).
A card keeps its number for good. Deleting a card does not free its number, and moving it between columns never changes it.
With a connected repository, a key in a commit message, a branch name or a pull request links it to the card. See /help/boards/board-webhooks-and-repositories.
A key only ever finds a card in the workspace you are in, on a board you can open.
A board remembers its 5 most recent earlier keys, and no other board in the workspace can take one of them. A board that moves to another workspace keeps its key if it is free there.
What happens next: the new key shows on every card at once, and the earlier key still opens the same cards.

If something goes wrong

"Another board in this workspace uses that key.": choose another.
"A board key is 2 to 8 capital letters and digits, starting with a letter."
A key finds nothing: the card is in another workspace, or on a board you cannot open.