DNS is the system that turns a site name such as vimeo.com into the numeric IP address your device actually connects to.
Explanation
Before your browser can open any website it has to ask a DNS resolver one question: which IP address belongs to this name? The resolver is normally chosen by your network, usually your ISP or office router, unless you set a public one such as Cloudflare's 1.1.1.1 or Google's 8.8.8.8. Classic DNS travels unencrypted on port 53, so whoever runs the network can read the names you look up and can also answer them falsely. That makes DNS the cheapest place to block a site: the ISP simply replies with a wrong address. OONI measurements show this happening right now. On 14 October 2026 a test on Iran's Mobinnet network (AS50810) asked for vimeo.com and received 10.10.34.36, a private address that leads nowhere, instead of Vimeo's real servers. In Turkiye, OONI saw TurkNet answer lookups for YouTube with 195.175.254.2, an address associated with blocking. Changing resolver or using encrypted DNS defeats this kind of block, but not blocks based on the site's IP address or its TLS name. Through a web proxy, your device only looks up the proxy's own name; the lookup for the site you open happens on the proxy server, outside your network.
In practice
A real DNS block, read straight from OONI's raw data: on 14 Oct 2026 at 20:38 UTC, a probe on Mobinnet (AS50810) in Iran asked its system resolver for vimeo.com and got back 10.10.34.36. OONI classed it as a confirmed block with 'dns inconsistent', because resolvers outside Iran return Vimeo's public addresses. In OONI's 15 Jul - 15 Oct 2026 window, 3,453 of 7,220 Iranian tests of vimeo.com were confirmed blocks. Turkiye's TurkNet used the same trick on YouTube in September 2025, answering with 195.175.254.2.
Sources: OONI measurement: vimeo.com on Mobinnet AS50810, 14 Oct 2026 (DNS answer 10.10.34.36) · OONI Explorer: vimeo.com tests in Iran, 15 Jul - 15 Oct 2026 · OONI — Throttling of social media in Turkiye (20 Nov 2025)
Measured · 2026-10-05
15 public DNS resolvers queried via DomainScan.
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