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Develop in Production

ILC allows you to develop your micro frontends in the context of the production environment. It means that you can render your new application or change the version of the existing one directly at the production website.

With this approach, you can see the final result faster without the need to mock other micro frontends inside your local development environment (LDE).


This example shows how to develop your application within the demo site.

Imagine that you are trying to substitute the News application with the one that is launched locally, considering that the demo site is your production environment.

To do this:

  1. Run the demo applications locally. Follow the instructions from the "Development process" section .
  2. Expose your local applications:

    • If you don't have a "white" IP address, use ngrok or a similar tool.

      ngrok usage

      1. Download & install ngrok .
      2. Run ngrok http 8239 (as the News application uses the 8239 port).
      3. Use the exposed URL (it looks as follows:
    • If you do have a "white" IP address, use the following URL: http://your_public_ip:8239

  3. Open the demo site and add the following cookies:

    const exposedUrl = ''; // or http://your_public_ip:8239
    const overrideConfig = encodeURIComponent(JSON.stringify({
        apps: {
            '@portal/news': {
                spaBundle: exposedUrl + '/dist/single_spa.js',
                cssBundle: exposedUrl + '/dist/common.css',
                ssr: {
                    src: exposedUrl + '/news/?fragment=1',
                props: {
                    publicPath: exposedUrl + '/dist/',
    document.cookie = `ILC-overrideConfig=${overrideConfig}; path=/;`
  4. Refresh multiple times.

    • In the "Network" tab of the browser developer tools, ensure that part of the requests is passed to the URL specified in the exposedUrl variable.
  5. Make some changes in your local News application. For example:
    1. Go to the cloned ilc-demo-apps repository.
    2. Open the /apps/news-ssr/src/components/Home.vue file.
    3. Replace <h1>Pick a news source</h1> with <h1>Hello world</h1>.
    4. Navigate to the URL and check that the changes appeared on the Demo website (You should see the h1 heading with the "Hello world" text).
  6. Check that SSR works correctly:

    1. Turn off Javascript in your browser

    After reloading the page, you should still see the correct "Hello world" heading.

Security considerations⚓︎

The possibility of overriding ILC configuration for the browser using cookies introduces a risk of website defacement attack via XSS .

To mitigate this risk, ILC restricts (by default) all domains and real IP addresses specified for all links in configuration. Only private IPv4 addresses are allowed.

To allow specific origins, in the "Settings" page of the ILC Registry, set the overrideConfigTrustedOrigins property: - default: any origin is disallowed, except for private IPv4 addresses - all: trust any origins -, trust and only (recommended)

Create your MS⚓︎

  1. Take the adapter for your framework, wrap your application with it, and export lifecycle functions.
  2. Turn off CORS for the development environment.

    Webpack config to disable CORS
    devServer: {
        headers: {
            "Access-Control-Allow-Origin": "*",
  3. Wrap your MS bundle file with the following code:

    "(function(define){\n" + bundle_content + "\n})((window.ILC && window.ILC.define) || window.define);"

    For Webpack, you can use wrapper-webpack-plugin

  4. Make sure your MS is publicly available - that is, hosted under (default for Node http, and Express ) and exposed via your public IP address or with the help of specialized tools, like ngrok.

  5. Add ILC-overrideConfig cookie with the following configuration to production:

    const overrideConfig = encodeURIComponent(
            "apps": {
                // rewrite the existing MS
                "@portal/NAME1": {
                    "spaBundle": "", // url to bundle
                    "ssr": {
                        "src": "", // url to ssr
                // add new MS
                "@portal/NAME2": {
                    "spaBundle": "", // url to bundle
                    "ssr": {
                        "src": "", // url to ssr
                        "timeout": 1000,
                    "kind": "primary",
            // add new MS slot to certain route
            "routes": [
                    "routeId": 103,
                    "route": "/example/",
                    "next": false,
                    "slots": {
                        "body": {
                            "appName": "@portal/NAME2",
                            "kind": null
    document.cookie = `ILC-overrideConfig=${overrideConfig}; path=/;`
  6. Check that requests are not affected by the mixed content issue. If yes, you can turn off this check in your browser .

  7. If you excluded some libraries (for example, via the externals property of the webpack configuration), comment it when developing in production.

Shared libraries⚓︎

Shared libraries are developed the same way as MSs. You only need to provide library name (without @sharedLibrary/ prefix) and path to spa-bundle:

const overrideConfig = encodeURIComponent(
        "sharedLibs": {
            "sampleLibrary": {
                "spaBundle": '',

document.cookie = `ILC-overrideConfig=${overrideConfig}; path=/;`
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