polyfill.io is the original service by Jonathan Neal that our service is based on. It is shortly to be decommissioned.

cdn.polyfill.io is our new service, the subject of this HN thread, and a collaboration between Jonathan Neal and the FT.

polyfills.io is an unaffiliated project by Jonathan Ong.

The naming is confusing. Hopefully it will be clearer when we're able to decommission the original polyfill.io, and I've asked Jonathan Ong to consider renaming his.