After a few months of downtime (sorry!), the DNS tester is back.
It no longer uses the full list of nameservers from public-dns.tk, as it appears that someone is zmapping the entire IPv4 submitting every DNS server they find to the database (this was the cause of the downtime - my importer couldn't handle the large volume). Consequently the quality of data is now relatively poor and includes many dynamic addresses etc. For now I'm just using a subset of the servers (those that have been up reliably for at least several months), which should be good enough.
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