PascalCase, the case of classes
PascalCase, also called UpperCamelCase, capitalises every word including the first: FileManager. It is the convention for class, interface and type names in nearly every object-oriented language. The name honours the Pascal language, which popularised it.
Where you actually meet it
Beyond classes: React components (MyComponent), TypeScript types, C# enums and component filenames. The convention is so entrenched that React uses it to tell a component from an HTML tag — <div> is HTML, <Div> is a component.
Frequently asked questions
How does it differ from camelCase?
Only the first letter: lowercase in camelCase, uppercase in PascalCase. Everything else is identical.
Why does React require PascalCase?
Because JSX distinguishes components from HTML tags by case. A lowercase name is treated as a standard tag and your component will not render.
How are acronyms handled?
A run of capitals is treated as one word: XMLHttpRequest becomes XmlHttpRequest, not X_M_L…