Classes vs. IDs in HTML/CSS

Basic Concepts of Selectors

When working on web projects, CSS classes and IDs both used to style HTML elements, but they serve different purposes. IDs are like Student Numbers Totally unique to one person. while Classes are like group names. Lots of people can be in the “Developer” class. So, if there's a specific section or element that needs distinct styling or behavior, an ID is the go-to choice, otherwise if you want share the styles or behavior to the multiple element or groups, Classes is common choice for being reusable selector.

CSS Specificity Hierarchy

We thought CSS IDs were a top priority for modifying an object, but they’re really not. Inline styles (ex. style="...") have the highest priority because the style is right there on the element itself, which the browser reads immediately. Then CSS IDs (ex. #header) come after because they identify the element uniquely, but with less priority than inline styles since those are more specific.

Next are CSS classes (ex. .button{ }), which target multiple elements. They have a moderate level of specificity while staying flexible for reusing styles. Lastly, Element selectors (ex. div{ }, p{ }) have the lowest specificity because they target broad groups and don’t differentiate individual elements.