Questions about the check
The tool is on the home page. These answers describe the two signals it actually collects.
Does the check run from my connection or from a server?
The request to the website runs in your browser, on your current connection. That is deliberate: “down for me” and “down everywhere” are different problems. The name lookup goes to Google's public DNS, or to Cloudflare's if Google does not answer. Those resolvers are not the same thing as your ISP's resolver, so a split-horizon or filtered name can disagree with what your computer would look up on its own.
Why is there no HTTP status code?
A page is not allowed to read another site's response body or status. The check uses a request that only reports whether the browser got any reply. A reply can be a normal page, a 404, a 500, or a block page. If you need the status code, open the address yourself and look at the browser's network panel, or run a check from a server you control.
The check says responding, but I still cannot use the site. Why?
The host answered. The application on top of it may still be failing: a broken script, a login loop, an error that only appears after you sign in, or a regional block that still returns a page. Reload once, try a private window, then try another device. If the HTML never arrives, you would have seen the unreachable result instead.
DNS resolved, but the browser check failed. What does that mean?
The domain name points at an address, so the outage is not “this domain does not exist.” Your browser still could not finish a connection in 8 seconds. Causes include a downed server, a firewall that drops your network, a certificate problem, or an HTTP address blocked because this page is on HTTPS. Try the same host on mobile data before you file an outage report.
What is NXDOMAIN?
It is the DNS way of saying “this name is not here.” Typos cause it. So do expired domains and hostnames that only exist inside a company network. If both the A and AAAA lookups return NXDOMAIN and your browser also fails, other people using public DNS will fail too.
Will this work for a site that blocks automated checks?
The reachability request is made by your browser, with no custom user-agent from a datacenter. Many bot walls still return a page, which this tool counts as a response. Some networks simply drop the connection. The result will say the browser got nothing, and it will not invent a reason.
Do you store the addresses I check?
This site has no account and no lookup history. The hostname is included in the DNS query those public resolvers receive. Your browser then contacts the URL directly, with the referrer stripped so this site's address is not sent along. Details are in the privacy notice.
Can I paste an IP address instead of a domain?
Yes. Include http or https if you need a specific scheme. The DNS section is less meaningful for a raw address, because the useful question is whether your browser can open it. Private addresses such as 192.168.x.x only describe your own network.
How is this different from an uptime monitor?
A monitor runs on a timer from machines in a data centre and tells you when a check starts failing. This page runs once, when you press Check, and only from the browser in front of you. Use it to separate “my connection cannot get there” from “the name is not in DNS.” It will not email you later.