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.
How to monitor SSL certificate expiry
Auto-renewal fails quietly, and a calendar reminder doesn't know the cron broke. Three ways to watch certificate expiry, from a one-liner to automatic.
- basics
- ssl
How to set up uptime monitoring (in about ten minutes)
What to monitor, which check types to use, how often to check, and who should be woken up - four decisions, then the setup itself takes minutes on any monitor.
- basics
ERR_SSL_PROTOCOL_ERROR: what it means and how to fix it
The TLS handshake itself failed - usually a server speaking plain HTTP on port 443, or offering only protocol versions browsers now refuse.
- ssl
My site is up for me but down for others
When a site works on your machine and fails for everyone else: DNS caches, hosts files, IPv6, CDN regions - how to find which split it is.
- connectivity
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 (or if 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