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By default, Wrangler bundles your Worker code using esbuild. This means that Wrangler has built-in support for importing modules from npm defined in your package.json. To review the exact code that Wrangler will upload to Cloudflare, run wrangler publish --dry-run --outdir dist, which will show your Worker code after Wrangler’s bundling.

​​ Files which will not be bundled

Bundling your Worker code takes multiple modules and bundles them into one. Sometimes, you might have modules that should not be inlined directly into the bundle. For example, instead of bundling a Wasm file into your JavaScript Worker, you would want to upload the Wasm file as a separate module that can be imported at runtime. Wrangler supports this for the following file types:

  • .txt
  • .html
  • .bin
  • .wasm

Refer to Bundling configuration to customize these file types.

For example, with the following import, the variable data will be a string containing the contents of example.html:

import data from "./example.html"; // Where `example.html` is a file in your local directory

This is also the basis of Wasm support with Wrangler. To use a Wasm module in a Worker developed with Wrangler, add the following to your Worker:

import wasm from "./example.wasm"; // Where `example.wasm` is a file in your local directory
export default {
fetch(request) {
const module = WebAssembly.instantiate(wasm);

​​ Conditional exports

Wrangler respects the conditional exports field in package.json. This allows developers to implement isomorphic libraries that have different implementations depending on the JavaScript runtime they are running in. When bundling, Wrangler will try to load the workerd key. Refer to the Wrangler repository for an example isomorphic package.

​​ Disable bundling

Opt out of bundling by using the --no-bundle command line flag: wrangler publish --no-bundle. If you opt out of bundling, Wrangler will not process your code and a number of features will not be available. You can use Custom Builds to customize what Wrangler will bundle and upload to the Cloudflare edge network when you use wrangler dev and wrangler publish.

​​ D1 bindings

During the beta period for D1, D1 bindings will not be available to a Worker published with --no-bundle.

​​ Editing via the Cloudflare dashboard

It is not possible to edit your Worker in the Cloudflare dashboard when you use the --no-bundle flag. The Cloudflare dashboard does not support Workers with multiple modules. If you use a Custom Build script, which bundles your Worker into a single module, this limitation can be bypassed.