Tailwind defines five breakpoints by default.

• sm640px
• md768px
• lg1024px
• xl1280px
• 2xl1536px

Similar to hover:, you can prefix any utility class with a breakpoint. When prefixed, a utility class only takes effect at that breakpoint and above.

For example, md:font-bold makes an element's text bold only from the md breakpoint and up. When the viewport is smaller than 769px, this utility class will have no effect.