What does "Only when Firefox is set to block known trackers" mean?

Does it mean that Firefox will only send a "Do Not Track" signal to the websites that are on the block list that Firefox uses when "Enhanced Tracking Protection" is set to block cross-site and social media trackers?

So "known trackers" is referring to the "block list" that Firefox uses when "Enhanced Tracking Protection" is set to block cross-site and social media trackers?

So if the above were true, then if I were to set ETP to "Custom" and set "Cookies" to anything other than "Cross-site and social media trackers", then Firefox would NOT send "Do Not Track" signals to websites?

And would also mean, that if ETP is set to block cross-site and social media trackers, but ETP was turned OFF, then Firefox would also NOT send "Do Not Track" signals to websites?

What about "Tracking content", "Cryptominers", and "Fingerprinters"? Are they also classified as "known trackers"?

"Do Not Track" only means that Firefox add "DNT=1" to the HTTP request headers, it is up to the website to respond to this request.

• https://support.mozilla.org/en-US/kb/how-do-i-turn-do-not-track-feature

See also:

• https://blog.mozilla.org/security/2021/03/23/introducing-smartblock/
• https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection

What does "Only when Firefox is set to block known trackers" mean?

Where is the setting that sets Firefox to block known trackers?

Is setting ETP to either "Standard", "Strict", or "Custom" how I set Firefox to block known trackers?

When using the setting "Only when Firefox is set to block known trackers", does this mean that if I turn OFF ETP, websites will NOT be sent a "Do Not Track" signal?

Here's the difference:

• Standard blocks: "Tracking content in Private Windows"
• Strict blocks: "Tracking content in all windows"
• Custom blocks: whichever you choose, or nothing if you uncheck the box

By the way, do you WANT to send the DNT signal, or do you NOT want to send the DNT signal?

A user was concerned that DNT makes their Firefox "fingerprint" a little more unique, so I created an extension that strips off DNT regardless of the Tracking Protection setting. It only has two users, so I suspect most people aren't worried about this...

https://addons.mozilla.org/firefox/addon/remove-dnt-donottrack-header/

Not sure yet if I want to send the DNT signal or not.

First I want to understand what the "Only when Firefox is set to block known trackers" setting does.

What does "Only when Firefox is set to block known trackers" mean?

If you block known trackers like cookies and other possible content from websites that are on a block list then it makes sense that you are interested in blocking content, so Firefox adds DNT=1 as well as an extra measure. If you do not block content (i.e. choose the custom mode with no ticks in any box) then there is no need to send this DNT signal to prevent losing content.

Not sure yet if I want to send the DNT signal or not. First I want to understand what the "Only when Firefox is set to block known trackers" setting does. What does "Only when Firefox is set to block known trackers" mean?

"known trackers"

Firefox has lists of tracking servers. These are the known trackers.

"set to block"

This is the "Tracking content" category:

• Standard blocks: "Tracking content in Private Windows"
• Strict blocks: "Tracking content in all windows"
• Custom blocks: whichever you choose, or nothing if you uncheck the box

"only when"

If you choose this option, then DNT is sent based on when Tracking content is blocked.