Your site loads fine from your desk, but a customer overseas says it will not open. Before you tear apart your server, check whether the block is happening in DNS, not on your site at all. A lot of country-level and network-level blocking works by refusing to resolve your domain, so the visitor never even reaches your server. This is different from your site being down, and you fix it in a completely different place.
How DNS-level blocking works
Every visitor resolves your domain through a DNS resolver, usually the one their internet provider hands them. Some countries and providers run filtered resolvers that return a wrong answer, or no answer, for domains on a blocklist. Indonesia's Nawala and similar national filtering systems are common examples: the domain resolves normally on an open resolver but returns a block page or an NXDOMAIN on the filtered one. The site is healthy. The path to it is being cut at the DNS step.
- Filtered resolver returns a block page. The domain resolves to an IP the provider controls, which shows a "this site is blocked" notice.
- Filtered resolver returns NXDOMAIN. The resolver pretends the domain does not exist. To the visitor it looks like a typo or a dead site. See the NXDOMAIN fix.
- The authoritative DNS is fine. Your nameservers still hand out the correct record to anyone who asks them directly. The block is downstream, at the visitor's resolver.
How to confirm it is regional DNS blocking
The tell is that the answer depends on who is asking. Check your domain from multiple locations and resolvers.
- Run a propagation check from many regions. If most regions resolve correctly but one country returns a block page or NXDOMAIN, that is filtering, not a DNS mistake on your end. Use the DNS propagation check and read propagation basics.
- Compare an open resolver against the local one. Ask a public resolver (like 1.1.1.1 or 8.8.8.8) and the visitor's provider resolver for the same record. A clean answer from the open resolver and a bad answer from the local one confirms it.
- Trace the delegation. Confirm your own nameservers are giving the right record so you can rule out a real DNS error. Run a delegation trace.
What you can and cannot fix
The uncomfortable truth is that you do not control someone else's resolver or a national blocklist. What you can do is make sure the block is not partly your fault and give affected users a path.
- Rule out your own DNS. A missing or wrong record can look like regional blocking. Confirm your A and AAAA records are correct everywhere first.
- Check if you are on a blocklist by mistake. Shared hosting IPs and previously-parked domains sometimes inherit a bad reputation. Review why links and domains get filtered.
- Request delisting where possible. National filters and some corporate filters have a review process for wrongly-blocked sites. It is slow, but legitimate business sites are often cleared.
- Give users an open-resolver option. Affected visitors can often reach the site by switching their device to a public DNS resolver, since the block lives in the provider resolver, not your server.
The one thing to remember
If a site works for most of the world but not one country or one network, suspect the resolver, not the server. DNS-level blocking happens before the request ever reaches you, so the fix is confirming your own records are clean and, where the block is a mistake, pursuing delisting. Start by proving your DNS is healthy everywhere with a full DNS test.