A few days ago, I wrote a post about how I built a bulk domain availability checker using PHP and RDAP (instead of the traditional WHOIS protocol) over at Site Tools Box .

To my surprise, the post got some fantastic technical feedback from the community. One comment from a developer named Furqan completely nailed some of the pain points I was already struggling with in production.

Here are the three brilliant suggestions he made, and how I'm currently implementing them to make the tool more reliable.

1. The "Premium Domain" Illusion: Why a 404 is Just a Hint

In my previous post, I mentioned that querying RDAP returns a 404 Not Found if a domain is available, and 200 OK if it's registered.

The problem? Premium and reserved domains. Sometimes, a registry will return a 404 because it's technically unregistered, but it's actually a premium name that requires a 5-figure price tag at the registrar.

Furqan's suggestion: Flag 404s as "Likely Available" instead of a hard "Yes".

This is a brilliant UX change.…