cra-template-ie11

This is an extension of the official base template for the create-react-app to offer base support for IE 11.

Specify the template 'ie11' (for example, --template @rdjennings/ie11).

Polyfills included via package.json"browserslist" spec

react-app-polyfill/ie11

react-app-polyfill/ie11 includes support for:

react-app-polyfill/stable

react-app-polyfill/stable includes additional functinoality not supported by IE11 and other browsers. By placing IE 11 in the browserslist section of package.json create-react-app will select the appropriate polyfills as needed.

ponyfill

cdn.jsdelivr.net/npm/css-vars-ponyfill@2

cdn.jsdelivr.net/npm/css-vars-ponyfill@2 is a ponyfill injected into the index.html in the public folder of the react app to provide CSS support for variables (all defined at the :root level). As a ponyfill it must be "activated" via call to "cssVars({})" using all of the default parameters. To see all of the options for this call visit:
https://jhildenbiddle.github.io/css-vars-ponyfill/#/

core.js

A great deal of the IE 11 support is dereived from core.js. For more information on what is supported visit:
https://github.com/zloirock/core-js/blob/master/README.md

NOTE:

CSS min, max (and by extension clamp) are still not supported. Other special handling, such as implicit grid placement, must be handled via the appropriate CSS