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Building Decentralized Applications with WebAssembly

By David Li on 2023-08-28T13:17:37.000Z

Building Decentralized Applications with WebAssembly

Decentralized applications (dApps) have gained significant attention in recent years, thanks to the rise of blockchain technology and the increasing need for more secure, private, and resilient solutions. In this article, we will explore how WebAssembly can be used to build dApps, providing an efficient and flexible platform for running code securely across various environments.

What is WebAssembly?

WebAssembly (Wasm) is a binary instruction format designed as a portable target for the compilation of high-level languages like C, C++, and Rust. It is a low-level virtual machine that runs code at near-native speed by using a compact binary format and a stack-based execution model. WebAssembly was initially created to enable web browsers to run complex applications with performance close to native, but its use cases have expanded beyond the browser to other environments such as blockchain and serverless computing.

Why Use WebAssembly for Decentralized Applications?

There are several reasons why WebAssembly is an excellent choice for building dApps:

  1. Performance: WebAssembly code is executed at near-native speed, which is crucial for computationally intensive tasks often found in dApps.
  2. Security: WebAssembly’s sandboxed execution environment provides strong isolation between the host system and the application, minimizing potential risks.
  3. Portability: WebAssembly is platform-agnostic, allowing developers to write code once and run it on various devices and environments.
  4. Language Flexibility: Developers can use their preferred programming languages, such as C, C++, Rust, and others, that can be compiled to WebAssembly.

Building a Decentralized Application with WebAssembly

Let’s go through the steps involved in building a simple dApp using WebAssembly:

Step 1: Choose a Blockchain Platform

First, you need to select a blockchain platform that supports WebAssembly smart contracts. Examples of such platforms include:

  • Ethereum: Ethereum 2.0 introduces support for WebAssembly-based smart contracts through its eWasm project.
  • EOSIO: A blockchain platform that natively supports WebAssembly smart contracts.
  • Polkadot: A multi-chain platform that allows developers to build and deploy WebAssembly-based smart contracts through its Substrate framework.

Step 2: Write the Smart Contract

Next, write the smart contract using a programming language that can be compiled to WebAssembly, such as Rust, C, or C++. For example, let’s create a simple smart contract in Rust that stores and retrieves key-value pairs:


use core::str::from_utf8;
use wasm_bindgen::prelude::*;

pub struct KeyValueStore {
    store: Vec<(String, String)>,

impl KeyValueStore {
    pub fn new() -> Self {
        Self { store: Vec::new() }

    pub fn set(&mut self, key: &str, value: &str) {
        for (k, v) in self.store.iter_mut() {
            if k == key {
                *v = value.to_string();
        self.store.push((key.to_string(), value.to_string()));

    pub fn get(&self, key: &str) -> Option<String> {
        for (k, v) in self.store.iter() {
            if k == key {
                return Some(v.clone());

Step 3: Compile the Smart Contract to WebAssembly

Compile the smart contract to a WebAssembly binary using a compiler like `car for Rust:

$ cargo build --target wasm32-unknown-unknown --release

Step 4: Deploy the Smart Contract

Deploy the compiled smart contract to the chosen blockchain platform. The process may vary depending on the platform, but usually involves submitting a transaction that includes the WebAssembly binary and any necessary metadata.

Step 5: Interact with the Decentralized Application

Finally, build a user interface (UI) to interact with the deployed smart contract. You can use web technologies like HTML, CSS, and JavaScript, along with libraries and frameworks such as React or Vue.js, to create a user-friendly UI.

To interact with the smart contract, you will need to use the platform’s SDK or API to send transactions and query the blockchain. These transactions will include calls to the WebAssembly functions exposed by your smart contract, such as set and get in our example.


WebAssembly offers an efficient, secure, and flexible platform for building decentralized applications. By leveraging its performance, security, and portability features,developers can create powerful dApps that run on various blockchain platforms and devices. As more platforms continue to adopt WebAssembly as a supported execution environment, it is poised to become a key technology in the future of decentralized applications and blockchain ecosystems. So, whether you’re a seasoned blockchain developer or just starting to explore dApps, consider using WebAssembly to bring your next decentralized application to life.

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