Windows 10 reached EOS (end of support) on October 14, 2025. If you are on Windows 10, see this article.

Search Support

Avoid support scams. We will never ask you to call or text a phone number or share personal information. Please report suspicious activity using the “Report Abuse” option.

Learn More
Open

stop FF doing DNS lookup when I hover over a link

mozilla888

I start FF in safe-mode. I open a local page which includes only one URL. When I hover on this link I see (`tcpdump`) a DNS lookup being performed for this domain. I followed the suggestions from Mozilla but I still see this.

How do I stop this access.

I use FF "156.0 (64-bit)" on Fedora 44.

TIA

I start FF in safe-mode. I open a local page which includes only one URL. When I hover on this link I see (`tcpdump`) a DNS lookup being performed for this domain. I followed the suggestions from Mozilla but I still see this. How do I stop this access. I use FF "156.0 (64-bit)" on Fedora 44. TIA

All Replies (4)

This is described in How to stop Firefox from making automatic connections section "Prefetching" › "Link prefetching" › "DNS prefetching": support.mozilla.org/en-US/kb/how-stop-firefox-making-automatic-connections#w_dns-prefetching

If the preferences documented there do not have any effect, it might be worth reporting either a pref bug, or a stale content at least. Thanks for checking.

Modified by jbr

Yes, what how-stop-firefox-making-automatic-connections recommends was done. Surely I am not the first person to notice this?

I will appreciate hearing from other people doing the same. I simply run

   $ sudo tcpdump -l port 53 -i eth1

where eth1 is the interface to my internet modem. Internal connections are on another interface.

I open this file

    
    the conversation
     

[unfortunately the editor is hiding my actual text. How can I insert unmolested text???]

I then move the focus (the mouse) to another window and hover over the link, briefly, and immediately see

09:09:56.218995 IP e7.eyal.emu.id.au.52426 > h.gtld-servers.net.domain: 47967% [1au] HTTPS? theconversation.com. (60) 09:09:56.219101 IP e7.eyal.emu.id.au.59252 > 120.19.253.254.domain: 11696+ [1au] A? theconversation.com. (48) 09:09:56.219326 IP e7.eyal.emu.id.au.48388 > 120.19.253.254.domain: 3849+ [1au] A? theconversation.com. (48) 09:09:56.396917 IP 120.19.253.254.domain > e7.eyal.emu.id.au.48388: 3849 4/0/1 A 151.101.66.132, A 151.101.130.132, A 151.101.194.132, A 151.101.2.132 (112) 09:09:56.396917 IP 120.19.253.254.domain > e7.eyal.emu.id.au.59252: 11696 4/0/1 A 151.101.66.132, A 151.101.130.132, A 151.101.194.132, A 151.101.2.132 (112)

This is followed by many other probes, but I am only interested in the start of this activity which is timed exactly with the hover. Maybe an add-on is still active, despite the --safe-mode? Some of the probes may be from my local bind, listening to 192.168.3.7. My resolv.conf includes:

   nameserver 192.168.3.7
   nameserver 120.19.253.253
   nameserver 120.19.253.254

Modified by mozilla888

Yes, what how-stop-firefox-making-automatic-connections recommends was done. Surely I am not the first person to notice this?

I will appreciate hearing from other people doing the same. I simply run

   $ sudo tcpdump -l port 53 -i eth1

where eth1 is the interface to my internet modem. Internal connections are on another interface.

I open this file

    
    the conversation
     

[unfortunately the editor is hiding my actual text. How can I insert unmolested text???]

I then move the focus (the mouse) to another window and hover over the link, briefly, and immediately see

09:09:56.218995 IP e7.eyal.emu.id.au.52426 > h.gtld-servers.net.domain: 47967% [1au] HTTPS? theconversation.com. (60) 09:09:56.219101 IP e7.eyal.emu.id.au.59252 > 120.19.253.254.domain: 11696+ [1au] A? theconversation.com. (48) 09:09:56.219326 IP e7.eyal.emu.id.au.48388 > 120.19.253.254.domain: 3849+ [1au] A? theconversation.com. (48) 09:09:56.396917 IP 120.19.253.254.domain > e7.eyal.emu.id.au.48388: 3849 4/0/1 A 151.101.66.132, A 151.101.130.132, A 151.101.194.132, A 151.101.2.132 (112) 09:09:56.396917 IP 120.19.253.254.domain > e7.eyal.emu.id.au.59252: 11696 4/0/1 A 151.101.66.132, A 151.101.130.132, A 151.101.194.132, A 151.101.2.132 (112)

This is followed by many other probes, but I am only interested in the start of this activity which is timed exactly with the hover. Maybe an add-on is still active, despite the --safe-mode? Some of the probes may be from my local bind, listening to 192.168.3.7. My resolv.conf includes:

   nameserver 192.168.3.7
   nameserver 120.19.253.253
   nameserver 120.19.253.254

Modified by mozilla888

Yes, what how-stop-firefox-making-automatic-connections recommends was done. Surely I am not the first person to notice this?

I will appreciate hearing from other people doing the same. I simply run

   $ sudo tcpdump -l port 53 -i eth1

where eth1 is the interface to my internet modem. Internal connections are on another interface.

I open this file

    
    the conversation
     

[unfortunately the editor is hiding my actual text. How can I insert unmolested text???]

I then move the focus (the mouse) to another window and hover over the link, briefly, and immediately see

09:09:56.218995 IP e7.eyal.emu.id.au.52426 > h.gtld-servers.net.domain: 47967% [1au] HTTPS? theconversation.com. (60) 09:09:56.219101 IP e7.eyal.emu.id.au.59252 > 120.19.253.254.domain: 11696+ [1au] A? theconversation.com. (48) 09:09:56.219326 IP e7.eyal.emu.id.au.48388 > 120.19.253.254.domain: 3849+ [1au] A? theconversation.com. (48) 09:09:56.396917 IP 120.19.253.254.domain > e7.eyal.emu.id.au.48388: 3849 4/0/1 A 151.101.66.132, A 151.101.130.132, A 151.101.194.132, A 151.101.2.132 (112) 09:09:56.396917 IP 120.19.253.254.domain > e7.eyal.emu.id.au.59252: 11696 4/0/1 A 151.101.66.132, A 151.101.130.132, A 151.101.194.132, A 151.101.2.132 (112)

This is followed by many other probes, but I am only interested in the start of this activity which is timed exactly with the hover. Maybe an add-on is still active, despite the --safe-mode? Some of the probes may be from my local bind, listening to 192.168.3.7. My resolv.conf includes:

   nameserver 192.168.3.7
   nameserver 120.19.253.253
   nameserver 120.19.253.254
Ask a question

You must log in to your account to reply to posts. Please start a new question, if you do not have an account yet.