I am using vue cdn of https://cdnjs.com/libraries/vue, They provide vue version that only support most newest version of browser.Please configure babel compile options to support legacy browser

[ghost]

https://cdnjs.cloudflare.com/ajax/libs/vue/3.3.4/vue.global.prod.min.js
This file contains let const ()=>{}, Most legacy browser does not support these syntax.

[jacekkarczmarczyk]

Legacy browsers don't support Proxy so you won't be able to use Vue 3 even if there's no let/const/arrow fn

[ghost]

This repo can polyfill Proxy for ie8 https://github.com/ambit-tsai/es6-proxy-polyfill

[Justineo]

There’s no guarantee that Vue can work with the polyfill. We are not going to transpile the distributed file to support legacy browsers that do not support arrow functions. If the proxy polyfill works for your case, we recommend you to transpile and publish your own fork.