Blog / Errors & fixes

Errors & fixes

What HTTP and DNS errors mean, why they happen and how to get a site back up.

ERR_CONNECTION_REFUSED: What It Means and How to Fix It

ERR_CONNECTION_REFUSED means nothing accepted the connection on that port. What it means at the TCP level, and fixes with curl, ss and firewalls.

7 min read

DNS_PROBE_FINISHED_NXDOMAIN: What It Means and How to Fix It

DNS_PROBE_FINISHED_NXDOMAIN means the domain name could not be resolved. Fixes for visitors and site owners, with dig and nslookup commands.

6 min read

My Website Is Down - A Step-by-Step Checklist

Website down? Work through DNS, TLS certificates, hosting, CDN, app errors, the database and recent deploys in order, with the exact commands to run.

5 min read

HTTP Status Codes - A Plain-English Reference for Monitoring

The common HTTP status codes from 1xx to 5xx, each with a plain-English meaning based on RFC 9110 and what it means for uptime monitoring.

7 min read

HTTP 504 Gateway Timeout - Causes, Timeouts and Fixes

A 504 Gateway Timeout means a proxy gave up waiting for the server behind it. Find the slow upstream, tune proxy_read_timeout, and fix the real cause.

5 min read

HTTP 503 Service Unavailable: Overload, Maintenance, Retry-After

HTTP 503 means a server is temporarily unable to handle requests. Learn the causes, how Retry-After works, and how monitoring should treat planned 503s.

5 min read

HTTP 502 Bad Gateway - What It Means and How to Fix It

A 502 Bad Gateway means a proxy got an invalid response from the server behind it. Learn the causes, the nginx log lines to look for, and the fixes.

5 min read

HTTP 500 Internal Server Error - Causes, Diagnosis and Fixes

What an HTTP 500 Internal Server Error means under RFC 9110, why your app returns it, and how to find the root cause in logs and fix it.

5 min read