I am looking to incorporate a domain name lookup facility in my website to make sure if a domain is available or not. The only api I could find on the net is http://www.domaintools.com/api/docs/domain-search/ . But this is paid. Is there any other api available which might be cheaper / free.I am working with php, query.
Domain Lookup API
api;domain name system
You can simply do DNS queries yourself. You would just have to always start at top (so called root servers) and work your way down the domain name, to be sure it does exist. Don't know what language you're using, but most languages out there have apropriate libraries for the job. Sure it requires some knowledge about DNS system itself, but since you are querying DNS system directly, you can be sure it is and will remain free.