User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:58.0) Gecko/20100101 Firefox/58.0 Build ID: 20180206200532 Steps to reproduce: THIS WAS POSTED HERE: https://support.mozilla.org/en-US/questions/1206970 This used to work, but now it doesn't. On both windows 7 and 10 x64 with Firefox Quantum. Try this: press ALT + w keys. You should press ALT, then w. Don't release ALT and keep pressing and releasing w. Now, when you want to stop release ALT (usually you release ALT after releasing w or at the same time). It's like doing ALT + TAB on windows. Actual results: Right now nothing happens, but before upon releasing ALT I was able to capture the moment when ALT key was released. The only way I can capture the release of ALT is if while pressing w, I release ALT first. Expected results: What I want is: press ALT and keep it that way, press w and release it, then release ALT. the message "combitation stop" should appear (in fiddle) Here is a fiddle to test jQuery: https://jsfiddle.net/e4berr36/1/ Vanilla JS: https://jsfiddle.net/e4berr36/9/ I'm expecting the same behaviour as if SHIFT is pressed, see: https://jsfiddle.net/e4berr36/10/

As jscher2000 said in the support forum (https://support.mozilla.org/en-US/questions/1206970#answer-1087585) I have a theory. When I test in the Extended Support Release of Firefox 52: about:support => Multiprocess Windows 1/1 (Enabled by default) press alt + W keydown fired: Alt keydown fired: w combitation detected keyup fired: w about:support => Multiprocess Windows 0/1 (Disabled) press alt + W keydown fired: Alt keydown fired: w combitation detected keyup fired: w keyup fired: Alt combitation stop

Test cases... me: w7/w10 x64 Firefox Quantum 58.0.2 x64 NOT WORKING coworker 1: w10 x64 Firefox Quantum 58.0.2 x64 NOT WORKING coworker 2: ubuntu 16.4 x64 Firefox Quantum 58.0.2 x64 WORKING AS EXPECTED coworker 3: macOS High Sierra 10.13.3 Firefox Quantum 58.0.2 x64 WORKING AS EXPECTED

I found two similar open bugs in a search for keyup alt (and no closed bugs): [e10s] Alt not firing keyup event if another key is pressed after keydown [Windows] https://bugzilla.mozilla.org/show_bug.cgi?id=1335347 Reported: 2017-01-31, New/Unassigned, P3 [e10s] missing keyup event for AltGr [regression] https://bugzilla.mozilla.org/show_bug.cgi?id=1435717 Reported: 2018-02-05, Unconfirmed

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:59.0) Gecko/20100101 Firefox/59.0 Hi Matias, thanks for reporting this issue. Tested this with Windows 10 x64 using Firefox Release 58.0.2 and Firefox Release 59.0.1 and I wasn't able to reproduce the issue you described. "Combination detected" text is displayed when pressing "Alt" and "w" keys. After releasing the keys, "combination stop" text is shown, as expected. I saw on the Support link from comment 0 that you already tried a new clean profile and safe mode and the issue is still reproducible on your side. Can you confirm this? Also, can you please open the "Browser Console" (Ctrl + Shift + J keys) and check if any errors are displayed while reproducing the issue? Please post them here if you see something is going wrong. Thanks.

Hello Carmen, I just upgraded to 59.0.1 (64-bits) and the issue persist. Also the browser console didn't display any errors while testing the fiddle. The important thing here is the sequence of keys being pressed and released: ISSUE ===== press ALT <<< "press alt + W" (default text) press "w" <<< "combination detected" release "w" <<< "combination detected" press "w" <<< "combination detected" release "w" <<< "combination detected" release ALT <<< (nothing happens) EXPECTED BEHAVIOUR ================== press ALT <<< "press alt + W" (default text) press "w" <<< "combination detected" release "w" <<< "combination detected" press "w" <<< "combination detected" release "w" <<< "combination detected" release ALT <<< "combination stop" PARTIAL WORKAROUND ================== press ALT <<< "press alt + W" (default text) press "w" <<< "combination detected" release "w" <<< "combination detected" press "w" <<< "combination detected" release ALT <<< "combination detected" release "w" <<< "combination stop"

Hi Carmen, could you try the following page that has a little more verbose reporting on keydown and keyup event detection: https://jsfiddle.net/e4berr36/20/ The scenario is press Alt, press w, release w, release Alt. As you normally would with Shift, Ctrl, or Alt (or a combination of those) and a letter key. Results for Firefox 59.0.1 with e10s enabled (default in new profile): press alt + W keydown fired: Alt keydown fired: w combitation detected keyup fired: w Results for Firefox 59.0.1 with e10s DISabled (browser.tabs.remote.autostart.2 => false): press alt + W keydown fired: Alt keydown fired: w combitation detected keyup fired: w keyup fired: Alt combitation stop

Does this have anything to do with bug 1446401?

Must not be related to bug 1446401. Sounds like that dup of bug 1335347 as comment 3 said.