What is EDNS Client-Subnet (ECS)?

EDNS Client-Subnet (ECS) is an extension to the DNS protocol to include components of the end-user IP address data in requests that are sent to the authoritative DNS servers. This means that there is a privacy “leakage” for recursive resolvers that send ECS data, where components of the end user’s IP address are transmitted to the remote site. This is typically used to improve the performance of Content Distribution Networks (CDNs).

NextDNS has invented and implemented a technology to prevent privacy “leakage” while keeping the performance benefit of ECS. While we think it is a good tradeoff, you still have full control on whether any ECS information is transmitted at all. For more information on our smart ECS technology, read How we made DNS both fast and private with ECS.

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