CSS Custom Property Polyfill Checker - Online IE11 Fallback
Paste your CSS and see a static fallback version where var() is replaced with the default value. For legacy support.
UD5 Toolkit
Paste your CSS and see a static fallback version where var() is replaced with the default value. For legacy support.
Demonstrate how to add custom headers and POST‑like functionality to EventSource using a polyfill. Code and example.