any, unknown, and never

Three special types with very different purposes:

• any — turns off type checking for that value entirely. Use it only as a last resort; it defeats the entire point of TypeScript wherever it's used.
• unknown — like any, it can hold anything, but you must narrow it (check its actual type) before doing anything with it — the safe version of "I don't know this type yet."
• never — a value that can never actually occur, such as a function that always throws or loops forever.

function process(value: unknown) {
    if (typeof value === "string") {
        console.log(value.toUpperCase()); // safe: narrowed to string
    }
}

Common mistakes

• Reaching for any to silence a type error instead of fixing the actual type mismatch — it's a compiler off-switch, and quietly disables checking anywhere it spreads.