What is the optimal width of a card? And responsive?

1. What width for mobile website?
2. How to design responsive card deck with fixed width in Bootstrap?

What width for mobile website?

It's best to make your website at least 1920px wide.

A 1280px website will look great on laptops and mobile devices but not so great on large monitors. To ensure your site looks just as good on big screens as it does on small screens, set your max site width to 1920px or more.

How to design responsive card deck with fixed width in Bootstrap?

For a Bootstrap 4 card deck with fixed-width cards, do this: Put each card into a column with the classes col-auto mb-3 (auto-width column + margin-bottom with three units). To center them, add the justify-content-center class to the row. The problem with this is that cards will have different heights.