What is .wasm?

.wasm files contain WebAssembly binary code, a low-level assembly-like language with a compact binary format that runs with near-native performance in modern web browsers. It provides a compilation target for languages like C, C++, Rust, and Go, allowing them to run on the web.

This quick guide explains when to use .wasm files, how to open them on any device, and how to share them instantly with FileXhost.

When to use .wasm files

You need high-performance code in the browser (e.g., video editing, 3D games, encryption).
You want to reuse existing C/C++/Rust libraries in a web application.
You are building a complex application that requires multithreading (via Web Workers).
You want to port a desktop application to the web.

How to open .wasm files

WASM files are binary and cannot be read with a text editor. You can view a textual representation (WAT) using tools like 'wasm2wat' from the WebAssembly Binary Toolkit (WABT).

Algorithm details

WebAssembly is a stack-based virtual machine. It is designed to be faster to parse and execute than JavaScript. The browser downloads the .wasm file, compiles it to machine code (often using a streaming compiler), and executes it alongside JavaScript.

Browser & platform support

Direct: Supported by all major browsers (Chrome, Firefox, Safari, Edge).
Integration: Loaded via JavaScript APIs like `WebAssembly.instantiateStreaming()`.

Format comparison

Feature	Details
Speed	Executes at near-native speed, significantly faster than JavaScript for heavy computations.
Language	Not written directly; it is a compilation target for other languages.
Security	Runs in a sandboxed execution environment, same as JavaScript.

How to create wasm files

Emscripten: Compile C/C++ to WASM.
Rust: Use `wasm-pack` to compile Rust code.
AssemblyScript: Write TypeScript-like code and compile to WASM.
Go: Use `GOOS=js GOARCH=wasm go build`.

How to convert wasm files

wasm2wat: Convert binary WASM to readable text format (.wat).
wat2wasm: Convert text format back to binary.

Advantages & disadvantages

Advantages

Near-native performance in the browser
Language agnostic (C++, Rust, Go, C#, etc.)
Secure and sandboxed
Portable across different platforms and architectures

Disadvantages

Binary format is not human-readable
Requires a bridge to interact with the DOM (JavaScript glue code)
Debugging can be harder than JavaScript (though sourcemaps help)

Tools & software

Compilers

Emscripten, Rust (cargo), Go, AssemblyScript

Inspection

WABT (wasm2wat), Chrome DevTools

Runtimes

Browsers, Wasmtime, Wasmer (for server-side)

Frequently asked questions

Does WASM replace JavaScript?

No. WebAssembly is designed to work *alongside* JavaScript. JS is still better for high-level logic and DOM manipulation, while WASM handles heavy computation.

How do I run a .wasm file?

You cannot double-click it. You need an HTML file with JavaScript that fetches and instantiates the WASM module.

Is it safe?

Yes. WebAssembly runs in the same secure sandbox as JavaScript and enforces same-origin policies.

Technical specs

File type: Code
Extension: .wasm
MIME type: application/wasm
Compression: Uncompressed
Max file size on FileXhost: Up to 25 MB per file on the free plan and up to 1 GB on Pro FileXhost accounts.

Upload your .wasm file to FileXhost to get a clean, shareable URL in seconds. View the file in a modern browser, protect access with optional settings, and let others download it without any confusing ads or cluttered file pages.

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