# Compiler vs Transpiler

URL: https://softwaredictionary.org/compare/compiler-vs-transpiler
Last updated: 2026-10-02

In short: A compiler turns code into a lower-level form a machine or VM runs, while a transpiler outputs another high-level language, like TypeScript to JavaScript.

## What is the difference between a compiler and a transpiler?

Both read source code and write out a translated version. A compiler usually goes down a level: C or Rust becomes machine code for a processor, and Java becomes bytecode for the Java virtual machine. A transpiler, short for source-to-source compiler, goes sideways: its output is code in another high-level language, or another version of the same one, that people could still read.

The difference is the target. A compiler produces something that runs directly, and much of its effort goes into optimizations such as inlining and register allocation. A transpiler produces source code for another tool to run, so it focuses on mapping features faithfully: TypeScript loses its types and becomes JavaScript, Babel rewrites modern JavaScript for older browsers, and Sass turns its syntax into CSS.

In practice the line is blurry, and a transpiler is really a kind of compiler. The TypeScript tool is literally called the TypeScript compiler, `tsc`, and some compilers, including the first C++ compiler, worked by producing C. What matters day to day is that transpiled code still needs a runtime, such as a browser or Node.js, and usually ships with source maps so that errors point back to the original file.

A common misconception is that transpiling makes code faster or checks it while it runs. A transpiler changes the form of the code, not what it does: TypeScript's types disappear from the output, and transpiled JavaScript runs at the speed of the JavaScript engine.

| Aspect | Compiler | Transpiler |
| --- | --- | --- |
| Output | Lower-level code: machine code or bytecode | Source code in another high-level language |
| Level | Goes down, toward the hardware | Stays at about the same level |
| Readable output | Not really; it is meant for machines | Yes, usually readable JavaScript or CSS |
| Main job | Optimizing and producing a program that runs | Mapping features between languages or versions |
| What runs the result | The processor or a virtual machine | Another runtime, such as a browser or Node.js |
| Examples | GCC, Clang, rustc, javac | tsc, Babel, SWC, Sass |

## Choose Compiler when

- You want a program that runs directly on the machine or on a virtual machine.
- Speed and build-time optimizations matter.
- You write in C, C++, Rust, Go or another compiled language.

## Choose Transpiler when

- You write TypeScript, JSX or modern JavaScript that must run in browsers.
- You want newer language features than your target platform supports.
- You turn one source language, like Sass, into another, like CSS.

## Frequently asked questions

**Is TypeScript compiled or transpiled?**

Both words are used. tsc is officially the TypeScript compiler, but because its output is JavaScript at the same level, calling it a transpiler is also correct.

**Is Babel a compiler?**

Babel calls itself a JavaScript compiler. What it does is transpile modern JavaScript and JSX into versions that older browsers and tools understand.

**Does a transpiler replace an interpreter?**

No. The transpiled code still needs something to run it, such as a browser's JavaScript engine, which may itself interpret or compile it.

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