[dns-operations] host.txt max size

Tomas L. Byrnes tomb at byrneit.net
Mon Jul 22 09:38:41 UTC 2019

Actually, there are discussions about that in the forum. The answer appears to be “depends”. Mostly it seems to depend on OS version and RAM. One rule of thumb I saw there was about 8,000 entries, but that was for XP 32 bit.

The site is not about running a local server version, but how to use a hosts file to perform filtering by FQDN, including discussion about the differences between using and as the entry.

It’s pretty exhaustive in its discussion, and rather than provide information that might not apply to the particular situation at hand, I thought it would be more helpful to direct you to the canonical source on the matter as it applies to Windows.

From: Irena Damsky <irena at damsky.tech>
Sent: Monday, July 15, 2019 2:53 AM
To: Tomas L. Byrnes <tomb at byrneit.net>
Cc: dns-operations at dns-oarc.net
Subject: Re: [dns-operations] host.txt max size

And yet it doesn't give you an indication of the file size that will make the machine unstable / resolution time per domain take forever.

I am looking for a solution that can be implemented on a windows machine and will not change the dns resolver setup, nor can I create a local server instance in this particular case.


On Sun, Jul 14, 2019 at 11:20 PM Tomas L. Byrnes <tomb at byrneit.net<mailto:tomb at byrneit.net>> wrote:
This site: http://winhelp2002.mvps.org/ has been providing resources to enable people to do exactly that for nearly 20 years.

From: dns-operations <dns-operations-bounces at dns-oarc.net<mailto:dns-operations-bounces at dns-oarc.net>> On Behalf Of Irena Damsky
Sent: Sunday, July 14, 2019 8:33 AM
To: dns-operations at dns-oarc.net<mailto:dns-operations at dns-oarc.net>
Subject: [dns-operations] host.txt max size

Hi team,

Looking for a quick a dirty solution for blocking malicious domains from a PC, wanted to use hosts.txt on a windows machine,
cannot seem to find any official resources that will mention the optimal maximum size for the file size - any suggestions?

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