Can't resolve 'crypto' in node_modules/bson/dist react

I’m using realm-web on my react app to build a simple task reminder app. But, when I start/build the app it is giving me a warning which says, can’t resolve ‘crypto’ in node_modules/bson/dist react. I’m attaching a screen snip for more info. The app is running fine but I’m having a problem when I deploy the app to Netlify. I have to configure the deploy settings to ignore warnings for now. I just want to know if it is possible not to get this warning in the first place and how to do it? Thanks in advance.


Hi @Subhash_Malireddy, I had the same issue and Iwas able to fix it.


I was using realm-web 1.6, I updated to 1.7 and the issue still appearing.

I basically did what the error message suggest, it doesn’t specify the file that you have to modify but looking around I’ve figured out that you need to add this line:
fallback: { "crypto": require.resolve("crypto-browserify") },

Into the file ./node_modules/react-scripts/config/webpack.config.js (line 304 to be precise in the react-scripts v5.0.0) so it looks something like this:

module.exports = function (webpackEnv) {
  return {
    resolve: {
      fallback: { "crypto": require.resolve("crypto-browserify") }

You also need to install the required modules:

npm install crypto-browserify
npm install stream

After this it built without warnings in my computer. :slightly_smiling_face:

Make it work in Netlify:

To make it work in Netlify I made a little bash script that edit the file and run it as a prebuild script.

  1. Created the bash script ./

line_to_add='fallback: { "crypto": require.resolve("crypto-browserify") }, // Patch realm-web crypto dependency'

echo "Fixing realm-web crypto dependency..."

if grep -q "$line_to_add" $webpack_config
    echo "Crypto fallback already added into the file $webpack_config"
    echo "Adding Crypto fallback into the file $webpack_config"
    cp $webpack_config $webpack_config_backup
    # The '\' character are for adding the indentation in the new line:
    sed -i "$line_number i \ \ \ \ \ \ $line_to_add" $webpack_config
echo "Done! realm-web crypto dependency fixed. You can now run 'npm run build' without warnings :)"
  1. Configure the script to be run before build in the package.json file, mine looks something like this:
  "scripts": {
    "start": "react-scripts start",
    "prebuild": "chmod +x ./; ./",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"

I hope it help you solve the issue.



Thanks for this fix Emiliano_Tortorella

Thanks very much! I’ve been procrastinating to fix this problem for a few weeks now and it’s now fixed thanks to your solution!