It's up now, but for how long?
One check only shows the status right now. ObserveOne checks your site every few minutes from 15 locations worldwide and alerts you the moment it goes down.
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Is it down for everyone, or just you?
The check does not run in your browser. When you press the button, our server makes the request from its own network, so what comes back is what a machine somewhere else sees. That is the whole point of asking a third party.
If the result says up and you still cannot load the page, the outage is on your side. Usual suspects: a stale DNS entry, a VPN, a corporate proxy, ISP routing, or a browser sitting on an old redirect. If the result says down, the site really is unreachable from outside, and there is nothing on your machine to fix.
What each result means
| Verdict | What the server saw | What it usually is |
|---|---|---|
| Up, 2xx or 3xx | A normal answer. Redirects are followed, so the code shown is where the chain ended, not where it started. | The site is serving traffic. |
| Up, 401 / 403 / 405 / 429 | Something answered and refused. Login required, a firewall rule, a method the server does not accept, or rate limiting. | Running but guarded. A dead host cannot refuse you. |
| Down, with a code | An error response. 408, 425, 500, 502, 503 and 504 are retried once before the verdict, because they often clear on a second attempt. | The application is broken or overloaded, not absent. |
| Down, code 0 | No HTTP response at all. DNS did not resolve, the connection was refused, or the TLS handshake failed. | Nothing is listening. Check the domain before the app. |
| Down, 408 timeout | The host took the connection and sent nothing back within fifteen seconds. | Usually an overloaded server rather than a dead one. |
If you want the response headers and the full redirect chain instead of a single verdict, the HTTP status code checker shows those.
Checking more than one site
There is no bulk field here, on purpose. One URL at a time gives you a real answer for the site you are actually worried about, which is what you want when the question is whether something is down right now. For a short list, paste them one after another.
If you find yourself doing that every morning, the problem is not the tool. Repeatedly checking the same set of sites by hand is what scheduled monitoring exists for, and no manual checker fixes it. The rest of the free developer tools cover the neighboring checks: certificates, DNS records, and security headers.
Frequently asked questions
Why does the checker say a site is up when I cannot reach it?
Because the request is made from our server, not from your machine. Two networks, two answers. When the server gets through and you do not, the fault sits between you and the site: a stale DNS entry, a VPN, a corporate proxy, ISP routing, or a browser holding an old redirect. Loading the site on a phone with wifi turned off usually settles it.
What does a status code of 0 mean?
Nothing answered. Zero is not an HTTP code. It is what we show when there was no HTTP response at all: the domain did not resolve, the connection was refused, or the TLS handshake failed. A site that returns 500 is broken. A site that returns 0 is missing.
Why is a site that returns 403 reported as up?
A server that refuses you is still a server that is running. 401, 403, 405 and 429 all mean something received the request and decided not to serve it, which is a permissions or rate limit problem rather than downtime. The checker sends an ordinary browser user agent, so a 403 here often just means the site blocks requests it does not recognize.
How long does it wait before calling a site down?
Fifteen seconds per attempt. It tries a HEAD request first because that is cheaper, then falls back to GET if the server rejects HEAD. The transient codes 408, 425, 500, 502, 503 and 504 get one retry, since those often clear on a second try. If the fifteen seconds run out with no response at all, the result comes back as a 408 timeout.
Does a fast response time mean the site is healthy?
No. The number is the time to one response from one location, and usually to a HEAD request at that. It says nothing about whether the page renders, whether checkout works, or whether users in another region see the same thing. A site can answer instantly and still be serving a broken cart.
Can I check several websites at once?
Not here. The tool takes one URL per check. For a list, run them in turn. If you are checking the same set of sites every morning, that is what scheduled monitoring is for rather than a manual tool.