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· 3 min read
Pascal Lapointe

If you are interested in both Web3, Cardano and cutting edge web app, you've probably already heard about Svelte and a Web3 library named Lucid. At the time of writing this post, both Svelte and Lucid are fairly new players, and they both share a common attribute: an efficient simplicity. Adastry’s UI leverages both and I loved the experience so far. Since I remember struggling a little getting started, I thought sharing my experience would help.

Quick start instructions

To get Lucid to work on SvelteKit, you must install and tweak a few things beforehand. Here's what I did to get in gear:

Installations Steps

Obviously, install Lucid library:

npm i lucid-cardano

Add support for the Node version of Fetch

Node fetch isn’t the same as your browser fetch API. If you intend to use Lucid on the browser side, install the fetch polyfill, otherwise svelte will complain at compile time:

npm i node-fetch-polyfill

Add WebAssembly support

Lucid leverages the Cardano Multiplatform Library written in Rust for fast computation. For this library you need to add WebAssembly support:

npm i vite-plugin-wasm

Add top level await support

Top level await has been supported since ES2022, but if you target an older JS version for compatibility like I do, you’ll need this work-around:

npm i vite-plugin-top-level-await

Config Files Updates

Now, adjust your vite.config.ts file accordingly with the libraries we just installed. Feel free to take out some parts if you don't need the fetch polyfill or the top level await plugin.

// vite.config.ts
import wasm from 'vite-plugin-wasm';
import topLevelAwait from 'vite-plugin-top-level-await';

const config: UserConfig = {
plugins: [sveltekit(), topLevelAwait(), wasm()],


resolve: {
alias: {
'node-fetch': 'node-fetch-polyfill',
optimizeDeps: {
esbuildOptions: {
target: 'es2020',
exclude: ['lucid-cardano'],
build: {
target: 'es2020',

Support for top level await has been added in recent javascript version, you might not require the top level plugin if you compile your code to a version after es2020. Just make sure you understand the implication regarding backward compatibility.


target: 'esnext',

Typescript configuration

If using typescript, make sure that the targeted JS version is the same in both vite.config.ts and tsconfig.json.

"extends": "./.svelte-kit/tsconfig.json",
"compilerOptions": {
"target": "ES2020"

And... Good to go!

The errors triggered by SvelteKit weren't so obvious when I researched this solution, so I hope it will save you some time. Let me know if you find anything missing to my instructions.

Happy coding!