Skip to main content

Web Assembly


Web Assembly is a faster image transformer that offers performance between the pureTransformer and sharpTransformer.

However, because Web Assembly uses additional code and setup, it must be installed separately.

If you would like to use Web Assembly, follow the steps below:


If you want to use a faster image transformer, install:

npm install -S remix-image-wasm
yarn add remix-image-wasm

Add To Your Loader Config

import type { LoaderFunction } from "remix";
import { imageLoader, DiskCache, MemoryCache } from "remix-image/server";
import { wasmTransformer } from "remix-image-wasm";

const config = {
selfUrl: "http://localhost:3000",
cache: new DiskCache(),
transformer: wasmTransformer

export const loader: LoaderFunction = ({ request }) => {
return imageLoader(config, request);

For an example project using Web Assembly, look at this example.

Add Wasm Files To Your Environment


Add the following lines to the bottom of your wrangler.toml file:

JPEG_ENC_WASM = "node_modules/remix-image-wasm/jpeg_enc.wasm"
JPEG_DEC_WASM = "node_modules/remix-image-wasm/jpeg_dec.wasm"
PNG_WASM = "node_modules/remix-image-wasm/png.wasm"
WEBP_ENC_WASM = "node_modules/remix-image-wasm/webp_enc.wasm"
WEBP_DEC_WASM = "node_modules/remix-image-wasm/webp_dec.wasm"
# AVIF_ENC_WASM = "node_modules/remix-image-wasm/avif_enc.wasm" # uncomment for AVIF support
# AVIF_DEC_WASM = "node_modules/remix-image-wasm/avif_dec.wasm" # uncomment for AVIF support

Reducing Bundle Size

Going over the Cloudflare Worker file size limit?

You can solve this by only including the .wasm files for image types you want to speed up transformation for.

  • Files ending with _dec.wasm are used for image inputs
  • Files ending with _enc.wasm are used for image outputs

Note: An exception is PNG, which uses a single png.wasm for image inputs and outputs.

If an input image is in a format that you haven’t included the .wasm files for in your environment, it will use the fallbackTransformer option, which is pureTransformer by default and supports JPEG, PNG, GIF, BMP, and TIFF images.


Let’s say we have a project that uses images that are JPEGs, PNGs, and WEBPs. We want our faster wasmTransformer to handle our PNG→PNG, WEBP→WEBP, and PNG→WEBP transformations, while letting any JPEG transformations (JPEG→JPEG, JPEG→PNG, PNG→JPEG, etc) be handled by the built-in pureTransformer so we don’t have to include the large JPEG_DEC.wasm and JPEG_ENC.wasm files in our bundled project.

Therefore, we want our supportedInputs to be:

  • MimeType.PNG
  • MimeType.WEBP

And our supportedOutputs to be:

  • MimeType.PNG
  • MimeType.WEBP

Which we can do by setting the [wasm_modules] field in the wrangler.toml file to:

PNG_WASM = "node_modules/remix-image-wasm/png.wasm"
WEBP_ENC_WASM = "node_modules/remix-image-wasm/webp_enc.wasm"
WEBP_DEC_WASM = "node_modules/remix-image-wasm/webp_dec.wasm"

Note: pureTransformer does not include any support for WEBP inputs or outputs. If you do not include WEBP_DEC.wasm or WEBP_ENC.wasm in your environment, your WEBP images will not be transformed by Remix-Image.