Guides
Website errors, explained and fixed
What an error message means, who can fix it, and the exact commands for nginx, Apache, PHP-FPM, WordPress and shared hosting. Written for the moment your site is down. Not sure what is wrong yet? Start with the website down checker.
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Your website is down. Here is what to do in the first 15 minutes.
Is it just you, is it DNS, the certificate, the server or your host? The order to check things in, the commands, and what to send your host.
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Server down: what to check first, and in which order
The server itself, not one website: ping, ports and SSH from outside, then load, memory, disk and services from inside, and what changed.
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502 Bad Gateway: causes and how to fix it
The web server runs, but the application behind it does not answer. Where to look in nginx, Apache and PHP-FPM, and what to send your host.
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503 Service Unavailable: overloaded or in maintenance?
The server is up but refuses to serve: overload, maintenance mode or a hosting limit. How to tell which one it is and what to do.
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504 Gateway Timeout: what it means and how to fix it
The backend answers, but too late. Where the time goes (PHP, database, an external API), which timeouts to raise and which not to.
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DNS_PROBE_FINISHED_NXDOMAIN: causes and fixes
The domain name does not resolve to an address. Fixes for visitors (DNS cache, resolver) and for owners (expired domain, missing record, nameserver change).
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ERR_CONNECTION_REFUSED: causes and how to fix it
The address resolves, but the server refuses the connection: no web server listening, a firewall, a wrong port. Checks for both sides and the fixes.
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"Your connection is not private": the SSL certificate warning
The browser blocks the site because of its certificate: expired, wrong name, broken chain or a wrong clock. Read the error code, fix it with certbot or at your host.
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The free tools go with the guides: the website down checker tells you whether the site is down for everyone, the SSL checker whether the certificate is the problem, and the SPF, DKIM and DMARC checker whether your mail will arrive. And when it is your own server: we fix it.
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