Assets TL;DR

You can automatically copy static assets (essentially files and folders) into your canister's filesystem during deploy by using the assets, assets_large and build_assets properties of the canister object in your project's dfx.json file.

Here's an example that copies the src/frontend/dist directory on the deploying machine into the dist directory of the canister, using the assets and build_assets properties:

    "canisters": {
        "backend": {
            "type": "custom",
            "main": "src/backend/index.ts",
            "candid": "src/backend/index.did",
            "candid_gen": "http",
            "build": "npx azle backend",
            "wasm": ".azle/backend/backend.wasm",
            "gzip": true,
            "assets": [["src/frontend/dist", "dist"]],
            "build_assets": "npm run build",
            "metadata": [
                    "name": "candid:service",
                    "path": "src/backend/index.did"
                    "name": "cdk:name",
                    "content": "azle"

The assets property is an array of tuples, where the first element of the tuple is the source directory on the deploying machine, and the second element of the tuple is the destination directory in the canister. Use assets for total assets under ~90 MiB in size.

The build_assets property allows you to specify custom terminal commands that will run before Azle copies the assets into the canister. You can use build_assets to build your frontend code for example. In this case we are running npm run build, which refers to an npm script that we have specified in our package.json file.

There is also an assets_large property that works similarly to the assets property, but allows for total assets up to ~2 GiB in size. We are working on increasing this limit further.

Once you have loaded assets into your canister, they are accessible from that canister's filesystem. Here's an example of using the Express static middleware to serve a frontend from the canister's filesystem:

import express from 'express';

const app = express();



Assuming the /dist directory in the canister has an appropriate index.html file, this canister would serve a frontend at its URL when loaded in a web browser.