Website monitoring · No. 01
Website availability check
In short
A website availability check shows whether your website loads for visitors and search engine crawlers: which HTTP status code the server returns and how fast it responds. A healthy response is 200. Server errors (5xx), timeouts and DNS failures mean people see a blank screen, ad clicks go to waste, and Google crawls less and eventually drops pages from search.
Contents
What is website availability?
Website availability is your server’s ability to answer a request from a browser or a search engine crawler and deliver the page. Every time someone opens a URL, the server returns a three-digit HTTP status code — a short technical message about the result. Visitors never see it, but that code is exactly how browsers and Google know what happened.
Status codes are grouped by their first digit: 2xx means success, 3xx a redirect, 4xx a problem with the request, and 5xx a problem on the server (MDN). Then there are failures with no status code at all: the server didn’t respond in time, the domain couldn’t be found in DNS, or the browser doesn’t trust the SSL certificate.
| Response | What it means | What the visitor sees |
|---|---|---|
200 OK | The page was delivered successfully | The normal page |
301 / 302 | The page has moved permanently or temporarily | The browser opens the new address automatically |
404 Not Found | There’s nothing at this address | A “page not found” message |
500 Internal Server Error | Something broke in the website code or on the server | A blank page or an error message |
503 Service Unavailable | The server is temporarily unable to handle the request | A maintenance page or an error |
| Timeout | The server didn’t respond within the allowed time | A page that never finishes loading |
| DNS error | The domain couldn’t be resolved to a server address | “This site can’t be reached” |
| SSL error | The certificate has expired or doesn’t match the domain | A “Your connection is not private” warning |
What happens when your website goes down?
The obvious cost is lost visitors and leads: someone who hits an error rarely comes back. If you’re running ads to your website, you still pay for clicks when the page doesn’t load. But some consequences only show up later — in Google Search.
Google treats server errors as a signal to ease off and visits your website less often:
“5xx and 429 server errors prompt Google’s crawlers to temporarily slow down with crawling. For Google Search, already indexed URLs are preserved in the index, but eventually dropped.”
Timeouts and DNS failures are just as dangerous, even though the server returns no status code at all. Google puts them in the same bucket as server errors — and reacts even faster:
“Google treats network timeouts, connection reset, and DNS errors similarly to 5xx server errors. […] already indexed URLs that are unreachable will be removed from Google’s index within days.”
Once the server starts returning 2xx again, Google gradually brings crawling back up to its usual rate (Google documentation). In other words, a short outage leaves no trace, but one that lasts several days can cost you rankings that take weeks to win back.
Even planned downtime has limits. The right response for maintenance is 503: as MDN puts it, this code means “the server is not ready to handle the request,” and it should be used for temporary conditions (MDN). Google recommends taking a website offline this way only briefly — “a few days at most” (Google documentation).
Visibility in AI answers
How does website availability affect visibility in AI answers?
A page that can’t be reached can’t show up in Google’s AI answers either, because AI Overviews and AI Mode follow the same rule as regular search:
“To be eligible to be shown as a supporting link in AI Overviews or AI Mode, a page must be indexed and eligible to be shown in Google Search with a snippet, fulfilling the Search technical requirements.”
The chain is direct: prolonged 5xx errors, timeouts or DNS failures make Google crawl your website less, and then drop unreachable pages from the index. A page that isn’t in the index can’t be a source for an AI answer in Google.
A blip of a few minutes rarely has consequences. The dangerous outages are the ones that drag on for days without anyone noticing — for example, when the website goes down every night during a backup or is unreachable only from certain networks.
Why do websites go down?
The causes are usually mundane and rarely have anything to do with an attack:
- Server overload. A rush of visitors after an email campaign or an ad push, bot traffic or heavy background jobs use up memory and CPU, and the server returns 503 or stops responding altogether.
- A CMS, theme or plugin update. An incompatible plugin or PHP version is the most common reason for a 500 error right after an update.
- Hosting problems. The paid plan has run out, the disk is full, or the provider is doing maintenance or migrating the server.
- DNS. After a change of hosting or DNS provider, the records still point to the old address, or the domain is no longer delegated. Google notes that DNS errors are most commonly caused by misconfiguration (Google documentation).
- An expired SSL certificate. Free Let’s Encrypt certificates are valid for 90 days by default (Let’s Encrypt FAQ), so if automatic renewal stops working, browsers will start showing warnings within a few weeks.
- An expired domain registration. The registrar switches off the domain’s DNS, and your website disappears along with your email. Learn more in our article on domain expiration monitoring.
A special case: the website works for you but not for your visitors. Your browser may be showing a cached copy of the page, your network may still be using an old DNS record, or your IP address may be on the firewall’s allowlist — while a firewall or CDN blocks visitors from other countries or mobile networks. That’s why availability should be checked from the outside, not from your own computer.
How to spot a website availability problem
More often than not, customers are the first to notice an outage. Here are the symptoms you should act on right away:
| What you see | Likely cause | What to do |
|---|---|---|
| A blank white page or “500 Internal Server Error” | A code error after a CMS or plugin update | Roll back the latest update and check the server error log |
| “503 Service Unavailable” at peak hours | The server can’t handle the load | Check hosting resources, caching and bot activity |
| The page keeps loading forever | A timeout: the server has hung or is overloaded | Contact your host and check background jobs |
| “This site can’t be reached” | A DNS error or an expired domain registration | Check your DNS records and the domain expiration date |
| “Your connection is not private” | An expired or invalid SSL certificate | Renew the certificate and set up automatic renewal |
| It works for you, but customers complain | Browser cache, or a firewall or CDN blocking some networks | Check the website from the outside and over mobile data, and review your security rules |
How to check website availability yourself
For a one-off check, a browser and a few free tools are all you need:
- Open the website in an incognito window and over mobile data rather than office Wi-Fi. That way you bypass the browser cache and see the website the way a new visitor does.
- Check the status code: open developer tools (
F12) → the Network tab → reload the page. The Status column in the first row should show200. - Click the padlock icon in the address bar and check the date your SSL certificate is valid until.
- In Google Search Console, open the Crawl stats report under Settings. It shows which responses Googlebot received and whether there were any host availability problems.
- Use the URL Inspection tool in Search Console to see whether Google can fetch the page right now.
- Or use the FullCheckApp “Website availability check” and get the results in a clear visual format.
A manual check only shows what your website looks like at that moment. You won’t catch an outage at night or over the weekend this way — that takes a regular automated check.
If you chose the last option, you’ve already made the right call: the check runs automatically, and you’ll be the first to know about any warning or critical issue.
What FullCheckApp checks
Once a day, at a time you choose and in your time zone, FullCheckApp opens your home page from the outside — just like a visitor would. There’s nothing to install on your website.
- HTTP status code — exactly what the server returned.
- Response time — how many milliseconds the server took to respond.
- Server error or timeout — flagged as a critical issue.
Report labels: green means OK, yellow means a warning, red means critical. You can set the severity of each check separately for every website. After each check, you get an email report, and critical issues are also sent to Telegram.
The server returned “503 Service Unavailable”: the website is temporarily not handling requests.
If your website sits behind a security service like Cloudflare, keep in mind that FullCheckApp doesn’t pretend to be Googlebot. To keep the firewall from blocking the check, add the service’s IP address to your allowlist. The cart, catalog and other key pages are covered by a separate inner page availability check, and loading speed by the website speed check.
FAQ
What’s the difference between a 500 and a 503 error?
A 500 error means something unexpected broke on the server — most often a bug in the website code after an update. A 503 means the server is temporarily unable to handle requests because of overload or maintenance. For planned downtime, 503 is the right code to return, but Google recommends keeping it up for a few days at most.
Why does my website load for me but not for my customers?
Your browser may be showing a cached copy of the page, your network may still be using an old DNS record, and your IP address may be on your firewall’s allowlist. Meanwhile, a firewall or CDN may be blocking your customers, or they may be reaching a different server. Check the website in incognito mode, over mobile data and with external tools.
Will my website drop out of Google if it was down for a few hours?
A short outage usually has no lasting effect: Google temporarily slows down crawling and gradually returns to the usual rate once the server responds normally again. The risk starts when errors last for days. According to Google’s documentation, indexed pages that stay unreachable are eventually dropped from the index — and with network errors, within days.
What is a timeout, and why is it a problem?
A timeout happens when the server doesn’t respond within the allowed time, so the browser never gets the page. The visitor sees a page that keeps loading and leaves. Google treats network timeouts the same way as 5xx server errors: it slows down crawling, and prolonged problems can get pages removed from the index.
Does website downtime affect AI Overviews?
Yes, indirectly. To appear in AI Overviews or AI Mode, a page has to be indexed and eligible to be shown in Google Search. Prolonged server errors, timeouts or DNS failures get pages removed from the index, and a page that isn’t indexed can’t be a source for an AI answer in Google.
Sources
- Google Search Central — How HTTP status codes, and network and DNS errors affect Google Searchdevelopers.google.com/search/docs/crawling-indexing/http-network-errors
- Google Search Central — Network and DNS errorsdevelopers.google.com/crawling/docs/troubleshooting/dns-network-errors
- Google Search Central — Pause or disable a websitedevelopers.google.com/search/docs/crawling-indexing/pause-online-business
- Google Search Central — AI features and your websitedevelopers.google.com/search/docs/appearance/ai-features
- MDN Web Docs — HTTP response status codesdeveloper.mozilla.org/en-US/docs/Web/HTTP/Reference/Status
- MDN Web Docs — 503 Service Unavailabledeveloper.mozilla.org/en-US/docs/Web/HTTP/Reference/Status/503
- Let’s Encrypt — FAQletsencrypt.org/docs/faq/
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