Outage & Reliability Glossary

Plain-English reference articles for the technical concepts behind website outages. These deep-dives complement our methodology page and the per-site status pages — when a site is misbehaving, these articles explain what the underlying error codes and protocols actually mean. For live status, check our current outages feed or browse all categories.

• Time to First Byte (TTFB) Explained: What It Measures and Why It Matters

  Time to First Byte (TTFB) is the latency between sending an HTTP request and receiving the first byte of the response. Plain-English explanation of what TTFB measures, what's good and bad, and how to improve it.

  Published April 29, 2026

• SSL/TLS Errors: Why They Break Websites and How to Fix Them

  Plain-English explanation of SSL/TLS errors — expired certificates, hostname mismatches, protocol incompatibilities, and chain-of-trust failures. How to diagnose them as a user and an operator.

  Published April 29, 2026

• HTTP 503 Service Unavailable: What It Means and How to Fix It

  HTTP 503 Service Unavailable means the server is intentionally refusing requests, usually because of overload or maintenance. Plain-English explanation of when it appears, why it differs from 502, and what to do.

  Published April 29, 2026

• HTTP 502 Bad Gateway: What It Means and How to Fix It

  HTTP 502 Bad Gateway means an upstream server returned an invalid response to a gateway or proxy. Plain-English explanation of the causes, how to diagnose them, and what to do — for both website visitors and operators.

  Published April 29, 2026

• DNS Resolution Explained: How a Domain Name Becomes a Website

  Plain-English explanation of how DNS resolution works, the role of recursive vs authoritative servers, why DNS failures are responsible for many website outages, and how to diagnose them as a user or operator.

  Published April 29, 2026