Guides
Plain answers for when a site is down: DNS, status codes, SSL errors, and how to tell a real outage from a problem on your side.
502 Bad Gateway: what it means and how to fix it
A 502 means your proxy is up but whatever sits behind it isn't answering properly. How to find which hop failed, with curl and log commands.
- http-errors
503 Service Unavailable: causes and fixes
A 503 is the server saying "alive, but not taking requests" — overload, maintenance mode, or failing health checks. How to tell which, fast.
- http-errors
504 Gateway Timeout: what it means and how to fix it
A 504 means the upstream didn't answer in time — too slow, not dead. How to find the slow hop, and why raising the timeout is rarely the fix.
- http-errors
DNS_PROBE_FINISHED_NXDOMAIN: how to fix it
Chrome's way of saying the domain name doesn't resolve at all. The four causes — typo, expired domain, broken records, stale cache — in order.
- dns
How to check if a website is down (and whether it's just you)
Four checks, in order: another network, DNS, a direct request with curl, and a look at the response itself. Two minutes, no tools to install.
- basics
SSL certificate expired: what happens and how to recover
Browsers hard-block expired certificates — every visitor sees a warning, not your site. How to confirm, renew, and never hit this again.
- ssl