Troubleshooting a Slow Board
Because Trello has to load open cards and attachments every time a board is opened, boards with a large number of open cards may see slower load times and generally reduced usability. We suggest having fewer than 1,000 open cards on any Trello board (and under 500 if there are a lot of attachments or checklists on the cards).
If you've noticed a board loading more slowly, we recommend the following options to improve performance:
Archive old/unused lists
If you have lists that you're no longer using every day, you can archive the list from the board. This will stop it from showing each time you open the board, but will allow you to un-archive the list if you ever need to, and to still search for those cards.
Archive old/unused cards
If you still need the list that the cards are on, but some of the cards themselves don't need to be actively referenced, you can archive individual cards (or archive all of the cards in the list at once in the list dropdown menu, leaving the list itself in place).
Move lists to a new board
If you are actively using all of your cards and lists, you can create a new board and split your content into multiple boards. This is helpful if you want an easily-referenced history board, or if a project has expanded beyond its original scope. Once you've made the new board, move the relevant lists to the new board.