In React, capitalizing component names is necessary because it helps distinguish between custom components and HTML elements.
When JSX is compiled, React uses the capitalization of the tag name to determine whether it is a custom component or a built-in HTML element.
Lowercase tag names (e.g., <div>, <span>) are treated as HTML elements.
Capitalized tag names (e.g., <MyComponent>) are treated as custom components.
If you write <myComponent /> (lowercase), React will look for an HTML element called <mycomponent>, which doesn't exist, and throw an error.
HTML elements are case-insensitive and always written in lowercase (e.g., <div>, <p>, <span>).
By capitalizing custom component names, you avoid naming conflicts with existing HTML elements.
<Button> is clearly a custom component.
<button> is an HTML button element.
React relies on tools like Babel to transform JSX into JavaScript. Babel uses the capitalization of component names to determine how to process them.
If you don't capitalize your component names, Babel might misinterpret them as HTML elements, leading to errors or unexpected behavior.