Compile-Time Error vs Runtime Error — What's the Difference?

A compile-time error is caught by the compiler (or a type checker) before the program ever runs, based on static analysis of the code; a runtime error occurs while the program is actually executing.

Why they differ

• Compile-time errors include syntax mistakes and, in statically typed languages, type mismatches — the program simply won't build until they're fixed
• Runtime errors include things like dividing by zero, accessing a null reference, or a network request failing — they can only be discovered as the program actually runs

How to choose

• Statically typed languages (like Java, TypeScript, Rust) catch many potential bugs at compile time, before the code ever runs
• Dynamically typed languages (like Python, JavaScript, Ruby) defer many of the same checks to runtime, trading earlier detection for faster iteration

FAQ

Can TypeScript eliminate runtime errors entirely?

No — TypeScript catches many type-related mistakes at compile time, but errors from things like a failed network request or invalid user input can still only be caught while the program runs.