What is the difference between unknown and any?

Both any and unknown can hold any value. The difference is what the compiler lets you do with it. any is assignable to everything and allows every operation, so errors propagate silently. unknown is assignable to almost nothing until you prove its shape with a check.

function parse(input: unknown): string {
  if (typeof input === "string") {
    return input.trim();
  }

  throw new Error("Expected a string");
}

const value: any = "text";
value.thisDoesNotExist();

Why unknown is safer

• unknown forces a runtime check before property access or calls
• any disables checking for the value and for everything derived from it
• unknown is appropriate for JSON, network responses and user input
• any is sometimes necessary at a library boundary, but it should be contained
• Prefer a validated concrete type over either one in application code

The danger of any is contagion. Once a value is any, properties read from it are any, function results are any, and errors disappear from the type checker. unknown stops that spread because every use requires narrowing first.