Why these tools
Each tool here does one job and explains the result. That matters because a raw answer — an IP address, a certificate, a status code — is only useful if you know what it means and what to change. Every page pairs the interactive tool with a clear write-up: what the record or header does, the common errors you will meet, and the steps to fix them.
They are built for the everyday problems that are annoying to diagnose: a domain that will not resolve, a certificate that expired, mail that keeps going to spam, a redirect loop, a page that feels slow because of caching, or a subdomain that quietly points somewhere unexpected. There is nothing to install and nothing to sign up for.
How it works
The static pages are served from a small web server while the actual lookups and checks run on a separate backend reachable over an encrypted connection. Queries are rate-limited and answers are cached briefly so the tools stay responsive and do not overload public DNS and web servers. Requests that could point at private or internal addresses are refused.
Privacy
No account is needed and the tools do not store a history of what you look up. The only analytics are anonymous page views; nothing is shared or sold. Each tool's page notes exactly what it does with your input.