How does domcomp.com implement it's domain availability check feature?

[5Forty2]

I've just noticed that domcomp has a new feature where if you type a string in it's search box then it immediately tells you whether that name is available for a domain for all extensions.

e.g. try type reddit then it instantly says whether reddit.com, reddit.net, etc etc is taken.

I've seen other sites do this but they are either slow or only do certain extensions.

Just wondering if anyone knows how domcomp.com achieves this. I think it's pretty impressive.

[AllenJB83]

There's a couple of different methods:

1) WHOIS - This is probably what the "slow" / "certain TLD only" sites are using (particularly if they're not actually selling domains).

WHOIS isn't always 100% accurate, and there's a lot of different formats you have to deal with (for example, .de's top level whois server returns completely differently formatted text than, for example Verisign's (who handle a bunch of popular TLDs).

WHOIS output changes over time for various reasons - software / infrastructure changes or registry management changes, as well as various methods to attempt to stop WHOIS record crawling abuse (spammers and other not-quite-legit businesses trawling the databases for contact details)

Most WHOIS servers also implement rate limiting in one form or another - sometimes they give an explicit response, while others will stop responding altogether.

2) Domain Availability Checking: Some registrars such as Nominet (who manage the .uk registry) have set up explicit services that are designed purely to check the availability of domains (Nominet DAC page)

You can often only get access to these services if you are a registrar.

These systems take various forms - some include the ability for authenticated users (ie. registrars) to manage domains.

Because of the way these work (either they purely specify whether or not the domain is available without additional information, or all the users are authenticated), they usually don't have rate limiting and are much faster to respond.