Hi

There is no comprehensive guide to the preferences on about:config. This is for two reasons:

There no need for most people to go anywhere near that part of Firefox and doing so could break their installation of Firefox. While there may be a preference that can temporarily solve a problem or is handy for testing a new feature, the users facing controls in the main user interface should be the ones that are used.

The preferences are changing on a regular basis, with new ones being added and old ones being removed. Given that most people do not need to go there, trying to keep track of the changes and update some kind of guide would only detract from the amazing work being done by many Mozillians globally.

Why are you curious about that preference?

You can discover the legal values for many preferences by searching in the source code. In this case:

https://searchfox.org/mozilla-release/source/modules/libpref/init/StaticPrefList.yaml#1158

That said, I turned off keyboard navigation across the toolbar (browser.toolbars.keyboard_navigation) because it slowed down how I use the tab key, so I haven't tested the effect this preference might have on tooltips displayed (or not displayed) when toolbar buttons are accessed using the keyboard.

That the preferences are changing on a regular basis is not a reason why they should not be documented. Documented source code is OK, if it is complete.

e.g.

1. 2 : user input depth (allow autoplay when the play is trigged by user input
2. which is determined by the user input depth)

What is user input depth? Is 'mouse hover' also 'user input'?

e.g.

1. 2 : user input depth (allow autoplay when the play is trigged by user input
2. which is determined by the user input depth)

What is user input depth? Is 'mouse hover' also 'user input'?

This is hard to understand. It seems the goal was to move to 1 (transient activation) but they couldn't quite figure out how to prevent sites from breaking:

• https://html.spec.whatwg.org/multipage/interaction.html#user-activation-data-model
• https://phabricator.services.mozilla.com/D73971

I think depth refers to whether the code attempting to play the video was called directly as a result of user input, or there was an intermediate function involved. As a possibly related scenario, I've run into a problem where an add-on needed to fetch information before taking an action and that asynchronous function call caused the extension to fail the user activation test.

Regarding mouseover, no, according to:

https://searchfox.org/mozilla-release/source/dom/base/UserActivation.h#126

That the preferences are changing on a regular basis is not a reason why they should not be documented.

Also some Preferences have been only temporary and hidden ones that you have to manually add in about:config (only worked when back-end existed for it in Firefox) and some Preferences defaults and or min/max values has changed over time to keep on top of that also.

There has been some efforts to document the Preferences in about:config like for example this old https://kb.mozillazine.org/About:config_entries KB article