If you are using the polyfill.io service for your website, you may want to reconsider. This was an amazing product, but the last maintainer sold the project and the domain to a China-based company without warning, and the domain is now pointing to a chinese IP running unknown code.
Birdside announcement by the project original author: https://twitter.com/triblondon/status/1761852117579427975
More context in a GitHub issue: https://github.com/polyfillpolyfill/polyfill-service/issues/2834