CSS is wild, really wild. And tricky. But let’s talk specifically about specificity.

When writing CSS, it’s close to impossible that you haven’t faced the frustration of styles not applying as expected — that’s specificity. You applied a style, it worked, and later, you try to override it with a different style and… nothing, it just ignores you. Again, specificity.

Sure, there’s the option of resorting to !important flags, but like all developers before us, it’s always risky and discouraged. It’s way better to fully understand specificity than go down that route because otherwise you wind up fighting your own important styles.

Specificity 101 #

Lots of developers understand the concept of specificity in different ways.

The core idea of specificity is that the CSS Cascade algorithm used by browsers determines which style declaration is applied when two or more rules match the same element.

Think about it. As a project expands, so do the specificity challenges. Let’s say Developer A adds .cart-button, then maybe the button style looks good to be used on the sidebar, but with a little tweak. Then, later, Developer B adds .cart-button .sidebar, and from there, any future changes applied to .cart-button might get overridden by .cart-button .sidebar, and just like that, the specificity war begins.