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LOBSTER WASM
File conversion

Convert LOBSTER to WASM

Verified by Adam B.· reviewed by FE Editorial ·updated Jul 12, 2026
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Is it possible to convert LOBSTER to WASM?
Yes - LOBSTER converts to WASM.

Because Lobster's WebAssembly target has no JIT, you first run --cpp to get C++, then build inside dev/emscripten with Emscripten's make to produce lobster.wasm plus its .js, .html, and .data files. The result runs in the browser via emrun.

Also to WASM: NMF

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Tested on macOS, Windows & Linux
Last verified Oct 2026

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Why convert LOBSTER to WASM?

Compiling to .wasm lets a Lobster game or graphical app run in the browser at near-native speed. Since Lobster's engine already supports WebAssembly, the Emscripten toolchain packages your compiled program and its assets into web-ready files.

How to convert LOBSTER to WASM

Lobster --cpp then Emscripten make OPEN-SOURCE

First run lobster --cpp my.lobster (the wasm build has no JIT), put your assets in dev/emscripten/assets, then in dev/emscripten run make -j8 to produce lobster.wasm, lobster.js, lobster.html, and lobster.data.

Run with emrun OPEN-SOURCE

Launch the built page with emrun --browser chrome lobster.html --verbose to test the WebAssembly build in a browser.

Emscripten toolchain FREE

Install and activate Emscripten (plus GNU make) beforehand, since the wasm build is driven entirely by Emscripten compiling Lobster's generated C++.

About these formats

.LOBSTER Lobster Source Code File

A .lobster file holds source code written in the Lobster programming language, a statically typed language with Python-like indentation created by Wouter van Oortmerssen and aimed mainly at…

Open .LOBSTER details →
.WASM WebAssembly Binary File

A .wasm file holds a compiled WebAssembly module: portable binary bytecode produced from languages like C, C++, or Rust and run at near-native speed. Most .wasm files are loaded by a web…

Open .WASM details →

Quality & what to watch

  • You can't skip the --cpp step - the WebAssembly build has no JIT, so the C++ compile is mandatory first.
  • The .wasm never travels alone: the browser needs the accompanying lobster.js loader, lobster.html page, and lobster.data asset bundle.
  • Assets must be placed in dev/emscripten/assets before the build so Emscripten packs them into lobster.data.

Frequently asked questions

Do I need to compile to C++ before WebAssembly?
Yes. Lobster's wasm target does not support the JIT, so you must run --cpp first and then build that C++ with Emscripten.
What files does the build produce?
Running make -j8 in dev/emscripten produces lobster.wasm, lobster.js, lobster.html, and lobster.data.
How do I run the wasm build?
Use emrun --browser chrome lobster.html --verbose to serve and open the page in a browser.
Can I ship just the .wasm file?
No. The browser also needs the .js runtime, .html loader, and .data asset bundle generated alongside it.