Make Firefox act like other browsers: keep AltGr as Alt for default shortcuts no matter the keyboard layout

Question

I have realized this is happening in Windows 10 as well as Linux, so I'm posting here.

I need to use AltGr in Firefox mainly as shortcut with back and forward arrows — for previous and forward page/address, something which is default in Firefox as well as in other internet browsers.

• In those other browsers, these shortcuts work with the keyboard layouts that I use — in Firefox they do work with the main one (English-US) but not with the others that I use: French, English-US international (just in Windows), English-US international with dead keys (just in Linux), and Romanian standard.
• I have tested this with a new, pure, addon-free profile of Firefox, as well as with some Firefox-based browsers (LibreWolf in Linux): the same thing happens.
• The other Alt-key (the "normal") one at the left of the keyboard works in all cases.

As I find myself often using different keyboard-layouts when navigating with Firefox, and because I am using AltGr+Arrows all the time, this becomes very confusing sometime.

How to troubleshoot this? What could the cause be? The fact that the keyboard is changed doesn't work as an explanation for the default shortcut to stop working.

**Should AltrGr count IN ALL CASES as a proper key for the default shortcut involving Alt? This seem to be the case in Chrome or Edge.

Or maybe this is normal, given AltGr "is primarily used to type characters that are not widely used"** But this only happens in Firefox.

The fact that in some layouts AltGr is the main modifier for special characters could be a sufficient explanation for what happens (AltGr would on such layouts be reserved for that purpose and stop acting as a normal Alt). For example, in US International, AltGr is indeed modifier for many special characters (with qwertyui ETC it gives äå®þüúíóö«»áßðø¶´¬æ©æ©ñµç¿); in French, in combination with ] it gives¤; on Romanian standard layout, with păîsdlșțâc,., it gives §[]ßđł'\©<>.

Why this is the case only in Firefox cannot be justified by this line of reasoning. Chrome, Chrome-based browsers, Edge of Microsoft, are very well able to keep providing the default shortcuts that I need with AltGr on all layouts without affecting the provision of special characters by those layouts.

Can this Firefox situation be changed by some setting in about:config?

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UPDATE:

As said in the answer (and discussed in a question like this), there are keyboard layouts that trigger the same problem in Chrome and other browsers, depending on the keyboard layout (and therefore my initial assumption that only Firefox was affected by such layouts is false). Only by change the layouts that I use (mentioned above) are affecting Firefox but not other browsers.

Answer 1

This behavior is correct - both the Alt and the AltGr keys are modifiers, but they are not identical.

The AltGr key is used as an additional Shift key, to provide a third and a fourth (when Shift is also pressed) grapheme for many keys. Most are usually accented variants of the letters on the keys, but also additional typographical symbols and punctuation marks. Some languages such as Bengali use this key when the number of letters of their alphabet is too large for a standard keyboard. On early home computers the alternate graphemes were primarily box-drawing characters.

Between AltGr and Shift, some keyboards can generate four different characters for the same key.

Firefox may choose to treat both as being the same, but other products are not obliged to follow.

The behavior of the AltGr key is therefore heavily dependent on the keyboard that is used (as you have found out).

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In answer to the change of the question:

If you have no use for the AltGr and would like it to be identical to the Alt key, you may use the following in Windows:

AutoHotkey script:

RAlt::LAlt

In Linux:

• In KDE/Plasma - select Right Alt key never chooses 3rd level under Key to choose 3rd level in the the advanced keyboard settings, as said here.

• In Gnome: as said here, in Gnome-tweak-tool - Typing - Key to choose 3rd level - Right Alt key never chooses 3rd level.