Is that website down?
Twenty tools tell you up or down. This one tells you up, and then what the up is hiding.
5 checks a minute and 20 an hour from one address, and 3 a minute for any given domain. Enough for a person, not enough to hammer a site through us.
What a checker answers, and what this one also answers
| The question you actually have | A usual is-it-down tool | This page |
|---|---|---|
| Did the server answer? | Yes, and well | Yes |
| Is the page readable, or did its stylesheet fail? | Not answered | Advantage: UptimeEZ. Nine layout signals, plus the page silhouette |
| Is a database error printed inside a valid page? | Not answered | Advantage: UptimeEZ. Matched against the engine signature list |
| Did the page quietly become noindex? | Not answered | Advantage: UptimeEZ. Checked on every pass |
| When does the certificate expire? | Sometimes | Advantage: UptimeEZ. Expiry date, chain and covered names |
| Is it down from Sydney as well as from Paris? | Advantage: the usual tools. Several probe locations | One location, ours |
| Was it down last night? | Advantage: the usual tools. History on the paid tiers | Not from this page. That needs monitoring |
Two rows go the other way, and they are the honest ones: a single probe location and no history are real limits of a one-off check.
Every reading above is counted in the engine source, which is public: src/Check/Css.php for the layout signals, src/Check/Database.php for the error signatures, src/Diagnose.php for what it tells you to do about them.
The same table with seven other tools in it , or what separates monitoring tools and how to test one.
The two rows above have a page each, because they are what a single reading cannot give you. Watching the page for change over time, and, if the site belongs to somebody else, a read-only link with their sites on it and nothing else.
The certificate row has a tool of its own now, because a date deserves more than one line: read a certificate on its own for the chain, the covered names and the domain expiry, or watch every certificate you are responsible for.
Questions people actually ask
Why does a site show as up when visitors say it is broken?
Because "up" only means the server answered. A WordPress site whose stylesheet failed to load answers 200 with a page that visitors cannot read. A site whose database is unreachable often answers 200 with the error printed inside an otherwise valid page. Counting the answer and reading the answer are two different jobs.
What does a 200 status code actually prove?
That something at that address returned a document. It says nothing about whether the document is the right one, whether it is readable, whether it still allows search engines to index it, or whether the certificate expires next week. Those are separate readings, and a checker that stops at the status code cannot make them.
Is the site down for everyone, or just for me?
This check runs from our server, not from your machine, so if it answers here and not for you, the problem is between you and the site: DNS cached on your side, a captive network, or a firewall rule. If it fails here too, the problem is on the site.
Can this tool be used to hammer a site?
No, and that took deliberate work. Five checks a minute and twenty an hour from one address, and no more than three checks a minute for any given domain whoever asks. That last limit is the one that matters: without it, a few hundred visitors each staying within their own quota would add up to a flood on one target, sent from our address.
Does one check tell me whether the site was down last night?
It cannot. A single reading describes one second. Answering "was it down at 3am" needs something that was already watching at 3am, which is the difference between a checker and monitoring.
You had to come here and type an address
Which means you already suspected something. Monitoring is the version where you hear about it first, and where the message says what to check rather than just that something broke.