What is class=“mb-0” in Bootstrap 4?

Question

The latest documention has:

<p class="mb-0">Lorem ipsum</p>

Q: What is mb-0?

Answer 1

Bootstrap has a wide range of responsive margin and padding utility classes. They work for all breakpoints:

xs (<=576px), sm (>=576px), md (>=768px), lg (>=992px) or xl (>=1200px))

The classes are used in the format:

{property}{sides}-{size} for xs & {property}{sides}-{breakpoint}-{size} for sm, md, lg, and xl.

m - sets margin

p - sets padding

---

t - sets margin-top or padding-top

b - sets margin-bottom or padding-bottom

l - sets margin-left or padding-left

r - sets margin-right or padding-right

x - sets both padding-left and padding-right or margin-left and margin-right

y - sets both padding-top and padding-bottom or margin-top and margin-bottom

blank - sets a margin or padding on all 4 sides of the element

---

0 - sets margin or padding to 0

1 - sets margin or padding to .25rem (4px if font-size is 16px)

2 - sets margin or padding to .5rem (8px if font-size is 16px)

3 - sets margin or padding to 1rem (16px if font-size is 16px)

4 - sets margin or padding to 1.5rem (24px if font-size is 16px)

5 - sets margin or padding to 3rem (48px if font-size is 16px)

auto - sets margin to auto

Read more in w3schools

Answer 2

It is used to create a bottom margin of 0 (margin-bottom:0). You can see more of the new spacing utility classes here: https://getbootstrap.com/docs/4.0/utilities/spacing/

Related: How do I use the Spacing Utility Classes on Bootstrap 4