Emscripten vs WebAssembly: What are the differences?

Introduction:

Emscripten and WebAssembly are both technologies that enable the execution of code in web browsers. However, there are some key differences between the two. This article will highlight the major differences between Emscripten and WebAssembly.

1. Compilation Process: Emscripten is a compiler toolchain that compiles C/C++ code into JavaScript, while WebAssembly is a binary instruction format for a stack-based virtual machine. Emscripten first translates C/C++ code into LLVM bitcode and then compiles it into JavaScript using the Emscripten compiler. On the other hand, WebAssembly directly compiles code into binary format, which is then executed in the browser.

2. Programming Languages Supported: Emscripten primarily supports C and C++ languages for compilation into JavaScript. It leverages LLVM as an intermediate representation to handle different programming languages. WebAssembly, on the other hand, supports a wider range of programming languages, including C, C++, Rust, and even languages like Python and Kotlin through additional tooling.

3. Performance: Emscripten compiles C/C++ code into JavaScript, which can be slower than native code execution. Although Emscripten provides optimizations and WebGL acceleration for certain operations, the performance is still limited by the JavaScript execution engine. On the other hand, WebAssembly provides near-native performance as it is designed to be executed at near-native speed, making it more suitable for computationally intensive tasks.

4. Code Size: Emscripten generates JavaScript code that is larger in size compared to the corresponding WebAssembly code. This is because JavaScript is a higher-level language, and the generated code may include additional runtime and compatibility features. WebAssembly, being a binary format, has a smaller code size, which improves loading speed and reduces bandwidth consumption.

5. Interoperability: Emscripten allows developers to interact with JavaScript code seamlessly. It provides a JavaScript API that allows invoking JavaScript functions from C/C++ code and vice versa. WebAssembly also supports interoperability with JavaScript, but it introduces a more efficient and direct interface for interaction, reducing the overhead involved in calling functions across the WebAssembly-JavaScript boundary.

6. Debugging and Tooling: Emscripten provides better debugging and tooling support compared to WebAssembly. Emscripten generates JavaScript code that can be easily debugged using standard web development tools like browser debugging consoles. WebAssembly, being a binary format, is not easily human-readable and requires additional tools like debugging extensions for accurate introspection.

In summary, Emscripten is a compiler toolchain that translates C/C++ code into JavaScript, providing better debugging and tooling support. WebAssembly, on the other hand, is a binary instruction format that offers near-native performance and supports a wider range of programming languages, with smaller code size and improved interoperability with JavaScript.