I'm also using Firefox 66 and it works for me. Here's a live example: https://mdn.github.io/js-examples/modules/basic-modules/ https://mdn.github.io/js-examples

I'm also using Firefox 66 and it works for me. Here's a live example: https://mdn.github.io/js-examples/modules/basic-modules/ https://mdn.github.io/js-examples/modules/basic-modules/ Source code and other examples are at: https://github.com/mdn/js-examples/tree/master/modules https://github.com/mdn/js-examples/tree/master/modules