Free ISP Check: Is a Site Down on Comcast, AT&T or Verizon?

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Please wait, we are opening the site from inside internet providers in the United States.
Checking providers in the United States0 s
    Finished
      Your IP:
      Report generated on
      Tested:

      Can each internet provider open the site?

        Load time on each provider

        Address lookup (DNS) Connect Secure handshake Server answer

        Other signals we checked

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          Enter a website. We open it from inside home internet connections on Comcast, AT&T, Verizon and other providers in the United States, tell you which ones can reach it, show where a broken route stops, and compare how fast it loads on each.

          ISP Check Overview

          Why does a site open on one provider but not on another?

          Every internet provider carries its customers' traffic over its own routes. If one link on the way is broken, filtered or overloaded, the site can fail for customers of that one provider while it works for everyone else. A provider's own DNS servers can also hand out a wrong or old address for the site.

          How does this ISP check work?

          We use test points that sit inside real home connections of providers in the United States. Each one opens your site the same way a visitor's browser would and reports whether it loaded and how long each part took. When a provider cannot open the site, we also trace the route from that provider and name the network where it stops. We also check whether the site's network is visible in the internet's route tables, and whether an outage is being reported for the United States or for the provider.

          How do I read the results?

          • The status line gives the short answer: the site is fine, it fails on some providers, it fails everywhere, or the problem is wider than the site.
          • Each provider gets a tick or a cross. For a cross, the route line shows the networks the traffic passed through and where it stopped.
          • The load time bars split each provider's time into address lookup, connect, secure handshake and server answer, so you can see which part is slow.

          If no test point is online inside a provider at that moment, that provider is listed as not tested rather than as failing.

          FAQs

          Each provider reaches your server over its own route. A broken or filtered link on the Comcast route, a firewall rule on your server that blocks Comcast addresses, or a wrong answer from Comcast's DNS servers can stop Comcast customers while AT&T customers are fine. The route line in the result shows where the Comcast traffic stops.

          No. The test runs from test points inside home connections of each provider, so the result does not depend on your own connection or location.

          It is the last network that answered before the traffic went quiet. When only one provider fails, that network is usually where the problem is. When every provider fails, the stop point usually just shows the server ignoring tests, and the site itself is the problem.

          Some providers carry traffic through another country or a busy exchange before it reaches your server. The load time bar shows whether the delay is in the address lookup, the connection, the secure handshake or the server's own answer.

          Every home provider in the United States that has a test point online at that moment, usually Comcast, AT&T, Verizon and several regional providers. A provider with no test point online is listed as not tested.

          ISP problems and practical fixes

          The route from that provider breaks before it reaches your server, or your server or firewall refuses that provider's addresses.

          How to fix: Check whether your hosting firewall, security plugin or country block is blocking that provider's network. If not, send your hosting company the network name where the route stops, so they can raise it with their upstream provider.

          When every provider fails, the problem is almost always the site itself: the server is down, its firewall blocks visitors, or its DNS points to the wrong address.

          How to fix: Check that the server and web service are running and that the domain's A record points to the right address. The Ping and Traceroute tools help confirm whether the server answers at all.

          Traffic from that provider may take a long detour, often through another country, before it reaches your server.

          How to fix: Host the site in the United States or put it behind a content delivery network with locations there. Ask your host whether they connect directly with that provider.

          The provider's DNS servers had to look up your domain from scratch, or your domain's own name servers answer slowly.

          How to fix: Use a fast DNS host with servers in the United States and keep a sensible TTL, such as one hour, so providers can reuse the answer.