We often get this question from customers who use one of our domain name portfolio management software.

The reason is that the whois databases are operated based on a thick model or a thin model. In the thick model, one whois server provides all the data corresponding to the domains. This model is used by ORG, BIZ, INFO, etc.

In the thin model there are two whois servers. The first whois server (at the registry)  provides only the basic details regarding a domain. It then points to the actual whois server that can provide full authoritative information. The second whois server (maintained by the registrar) has to be queried to get all the relevant data.

The thin model is used by “.com” and “.net” registries. So, for these domains there are two different whois queries there are two different expiry dates. In 99% of the cases these will be the same. However, in some cases this will be different and you may need to contact the registrar to fix any discrepancies.

For registries that use the thick model (org, biz, info, etc.) and for ccTLDs (country code TLDs), the software will only display the registry expiry dates. The registrar expiry column will be blank.

For registries that use the thin model, the software will display expiry dates corresponding to the two whois servers. These are labeled registry expiry and registrar expiry.