If example.com is zero-rated, does this include subdomains of the example.com domain, e.g. would books.example.com also be zero-rated or is zero-rating applied to the domain itself only?

  • 3
    You may want to explain "zeo-rated" where, by whom, under which scale... – Patrick Mevzek May 9 '20 at 17:34
  • For those of us that have never heard of it: Zero Rating: "the practice of providing Internet access without financial cost under certain conditions, such as by permitting access to only certain websites or by subsidizing the service with advertising or by exempting certain websites from the data allowance." – Stephen Ostermiller May 9 '20 at 19:29


If a provider zero-rates a domain, there's no guarantee that they zero-rate subdomains too. This is because as far as DNS is concerned, each subdomain is considered to be a completely separate fully qualified domain name.

If their zero-rating system is based on something other than DNS, then, again, there are no guarantees.

Edit: As Stephen mentioned in the comments, there may be good business reasons for a provider to zero-rate both a domain and all its subdomains. But that's a question of legal agreement, not a technical question.

  • It sounds to me that zero-rating is contract based. I'd think it depends on how the contract is written. Your "no guarantee" sounds right, but it also sounds perfectly plausible that companies would want to zero-rate their domain and all subdomains in some cases. – Stephen Ostermiller May 10 '20 at 10:15

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