diff --git a/css/leptonChrome.css b/css/leptonChrome.css
index a9f4c88a..a31ea8d2 100644
--- a/css/leptonChrome.css
+++ b/css/leptonChrome.css
@@ -79,12 +79,12 @@
     /* TARGET: original, photon */
     #TabsToolbar[brighttext]
       #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background:-moz-lwtheme,
     #TabsToolbar:not([brighttext])
       #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background {
       /* Nightly 96:  1px solid var(--tab-line-color, rgba(128,128,142,0.9)); */
@@ -214,20 +214,20 @@
   /*= Linux - Light System Default Theme's Selected Tab ========================*/
   @media (-moz-gtk-csd-available) and (prefers-color-scheme: light) {
     /* Because of
-      #TabsToolbar:not([brighttext]) #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab:is([visuallyselected=true], [multiselected]) > .tab-stack > .tab-background {
+      #TabsToolbar:not([brighttext]) #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab:is([visuallyselected], [multiselected]) > .tab-stack > .tab-background {
         border: 1px solid var(--tab-line-color, rgba(128,128,142,0.9));
         box-shadow: 0 0 4px rgba(128,128,142,0.5);
       }
      */
     #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background:not(:-moz-lwtheme) {
       box-shadow: 0 0 4px rgba(128, 128, 142, 0.5) !important;
     }
     #TabsToolbar:not([brighttext])
       #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background:not(:-moz-lwtheme) {
       box-shadow: 0 0 1px var(--tab-line-color, rgba(128, 128, 142, 0.9)), 0 0 4px rgba(128, 128, 142, 0.5) !important;
@@ -6765,7 +6765,7 @@
     )
     #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab[visuallyselected="true"]:not(:focus),
+    .tabbrowser-tab[visuallyselected]:not(:focus),
   :root:is(
       [lwtheme-mozlightdark],
       [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"]
@@ -6783,7 +6783,7 @@
     )
     #TabsToolbar:not([brighttext])
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
     --uc-tab-shadow-color: var(--uc-tab-shadow-color-bundle);
@@ -6796,7 +6796,7 @@
     )
     #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
     filter: drop-shadow(-1px 0px 0px var(--uc-tab-shadow-color, transparent))
@@ -7218,7 +7218,7 @@
   /* Remove side's background color border */
   #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
     --tabs-border-color: rgba(0, 0, 0, 0.3) !important;
@@ -7226,7 +7226,7 @@
   }
   #TabsToolbar:not([brighttext])
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background {
     box-shadow: 0 0 1px var(--tabs-border-color), 0 0 4px rgba(128, 128, 142, 0.5) !important; /* Original: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */
@@ -7690,7 +7690,7 @@
   }
   /* Fix tab overlap #678 */
   @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner") {
-    tab:where([visuallyselected="true"]) {
+    tab:where([visuallyselected]) {
       z-index: 1;
     }
   }
@@ -7739,14 +7739,14 @@
     --tab-label-mask-size: 30%;
   }
   #tabbrowser-tabs[closebuttons="activetab"]
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected="true"])
+    .tabbrowser-tab:is([visuallyselected], [multiselected="true"])
     .tab-label-container {
     --tab-label-mask-size: 25%;
   }
-  .tabbrowser-tab[visuallyselected="true"]:not([labelendaligned]):hover .tab-label-container,
+  .tabbrowser-tab[visuallyselected]:not([labelendaligned]):hover .tab-label-container,
   #tabbrowser-tabs:not([closebuttons="activetab"])
     > #tabbrowser-arrowscrollbox
-    > .tabbrowser-tab:not([visuallyselected="true"], [labelendaligned]):hover
+    > .tabbrowser-tab:not([visuallyselected], [labelendaligned]):hover
     .tab-label-container {
     --tab-label-mask-size: 0.9em; /* Original: 1em */
   }
diff --git a/css/leptonChromeESR.css b/css/leptonChromeESR.css
index f1e0eed8..47308a2b 100644
--- a/css/leptonChromeESR.css
+++ b/css/leptonChromeESR.css
@@ -79,12 +79,12 @@
     /* TARGET: original, photon */
     #TabsToolbar[brighttext]
       #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background:-moz-lwtheme,
     #TabsToolbar:not([brighttext])
       #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background {
       /* Nightly 96:  1px solid var(--tab-line-color, rgba(128,128,142,0.9)); */
@@ -344,20 +344,20 @@
   @media (-moz-gtk-csd-available) and (-moz-toolbar-prefers-color-scheme: light),
     (-moz-gtk-csd-available) and (prefers-color-scheme: light) {
     /* Because of
-      #TabsToolbar:not([brighttext]) #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab:is([visuallyselected=true], [multiselected]) > .tab-stack > .tab-background {
+      #TabsToolbar:not([brighttext]) #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab:is([visuallyselected], [multiselected]) > .tab-stack > .tab-background {
         border: 1px solid var(--tab-line-color, rgba(128,128,142,0.9));
         box-shadow: 0 0 4px rgba(128,128,142,0.5);
       }
      */
     #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background:not(:-moz-lwtheme) {
       box-shadow: 0 0 4px rgba(128, 128, 142, 0.5) !important;
     }
     #TabsToolbar:not([brighttext])
       #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background:not(:-moz-lwtheme) {
       box-shadow: 0 0 1px var(--tab-line-color, rgba(128, 128, 142, 0.9)), 0 0 4px rgba(128, 128, 142, 0.5) !important;
@@ -7177,7 +7177,7 @@
     )
     #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab[visuallyselected="true"]:not(:focus),
+    .tabbrowser-tab[visuallyselected]:not(:focus),
   :root:is(
       [lwtheme-mozlightdark],
       [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"]
@@ -7195,7 +7195,7 @@
     )
     #TabsToolbar:not([brighttext])
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
     --uc-tab-shadow-color: var(--uc-tab-shadow-color-bundle);
@@ -7208,7 +7208,7 @@
     )
     #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
     filter: drop-shadow(-1px 0px 0px var(--uc-tab-shadow-color, transparent))
@@ -7630,7 +7630,7 @@
   /* Remove side's background color border */
   #TabsToolbar[brighttext]
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background:-moz-lwtheme {
     --tabs-border-color: rgba(0, 0, 0, 0.3) !important;
@@ -7638,7 +7638,7 @@
   }
   #TabsToolbar:not([brighttext])
     #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background {
     box-shadow: 0 0 1px var(--tabs-border-color), 0 0 4px rgba(128, 128, 142, 0.5) !important; /* Original: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */
@@ -8102,7 +8102,7 @@
   }
   /* Fix tab overlap #678 */
   @supports -moz-bool-pref("userChrome.tab.bottom_rounded_corner") {
-    tab:where([visuallyselected="true"]) {
+    tab:where([visuallyselected]) {
       z-index: 1;
     }
   }
@@ -8151,14 +8151,14 @@
     --tab-label-mask-size: 30%;
   }
   #tabbrowser-tabs[closebuttons="activetab"]
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected="true"])
+    .tabbrowser-tab:is([visuallyselected], [multiselected="true"])
     .tab-label-container {
     --tab-label-mask-size: 25%;
   }
-  .tabbrowser-tab[visuallyselected="true"]:not([labelendaligned]):hover .tab-label-container,
+  .tabbrowser-tab[visuallyselected]:not([labelendaligned]):hover .tab-label-container,
   #tabbrowser-tabs:not([closebuttons="activetab"])
     > #tabbrowser-arrowscrollbox
-    > .tabbrowser-tab:not([visuallyselected="true"], [labelendaligned]):hover
+    > .tabbrowser-tab:not([visuallyselected], [labelendaligned]):hover
     .tab-label-container {
     --tab-label-mask-size: 0.9em; /* Original: 1em */
   }
diff --git a/src/compatibility/_os.scss b/src/compatibility/_os.scss
index 1acca2be..6557c556 100644
--- a/src/compatibility/_os.scss
+++ b/src/compatibility/_os.scss
@@ -192,7 +192,7 @@
 $_os_linuxDefaultShadow: 0 0 4px rgba(128, 128, 142, 0.5);
 @mixin _os_linuxDefaultThemeSelectedTab {
   #tabbrowser-tabs:not([noshadowfortests])
-    .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+    .tabbrowser-tab:is([visuallyselected], [multiselected])
     > .tab-stack
     > .tab-background:not(:-moz-lwtheme) {
     @content;
@@ -204,7 +204,7 @@ $_os_linuxDefaultShadow: 0 0 4px rgba(128, 128, 142, 0.5);
 @include OS($linux) {
   @include Light {
     /* Because of
-      #TabsToolbar:not([brighttext]) #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab:is([visuallyselected=true], [multiselected]) > .tab-stack > .tab-background {
+      #TabsToolbar:not([brighttext]) #tabbrowser-tabs:not([noshadowfortests]) .tabbrowser-tab:is([visuallyselected], [multiselected]) > .tab-stack > .tab-background {
         border: 1px solid var(--tab-line-color, rgba(128,128,142,0.9));
         box-shadow: 0 0 4px rgba(128,128,142,0.5);
       }
diff --git a/src/compatibility/_theme.scss b/src/compatibility/_theme.scss
index 418fad8d..d9173b04 100644
--- a/src/compatibility/_theme.scss
+++ b/src/compatibility/_theme.scss
@@ -64,7 +64,7 @@ menu {
   @each $prefix, $postfix in $options {
     #TabsToolbar#{$prefix}
     #tabbrowser-tabs:not([noshadowfortests])
-      .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+      .tabbrowser-tab:is([visuallyselected], [multiselected])
       > .tab-stack
       > .tab-background#{$postfix} {
       @extend %noneBorder;
diff --git a/src/tab/clipped_tab/_letters_cleary.scss b/src/tab/clipped_tab/_letters_cleary.scss
index 8b9f8997..2151dedd 100644
--- a/src/tab/clipped_tab/_letters_cleary.scss
+++ b/src/tab/clipped_tab/_letters_cleary.scss
@@ -24,12 +24,12 @@
   .tab-label-container {
     --tab-label-mask-size: 30%;
   }
-  &:is([visuallyselected="true"], [multiselected="true"]) .tab-label-container {
+  &:is([visuallyselected], [multiselected="true"]) .tab-label-container {
     --tab-label-mask-size: 25%;
   }
 }
 
-.tabbrowser-tab[visuallyselected=true]:not([labelendaligned]):hover .tab-label-container,
-#tabbrowser-tabs:not([closebuttons=activetab]) > #tabbrowser-arrowscrollbox > .tabbrowser-tab:not([visuallyselected=true],[labelendaligned]):hover .tab-label-container {
+.tabbrowser-tab[visuallyselected]:not([labelendaligned]):hover .tab-label-container,
+#tabbrowser-tabs:not([closebuttons=activetab]) > #tabbrowser-arrowscrollbox > .tabbrowser-tab:not([visuallyselected],[labelendaligned]):hover .tab-label-container {
   --tab-label-mask-size: 0.9em; /* Original: 1em */
 }
diff --git a/src/tab/newtab_button/_looks_like_tab.scss b/src/tab/newtab_button/_looks_like_tab.scss
index ef6e1038..c1fbc918 100644
--- a/src/tab/newtab_button/_looks_like_tab.scss
+++ b/src/tab/newtab_button/_looks_like_tab.scss
@@ -146,7 +146,7 @@
 
 /* Fix tab overlap #678 */
 @include Option("userChrome.tab.bottom_rounded_corner") {
-  tab:where([visuallyselected="true"]) {
+  tab:where([visuallyselected]) {
     z-index: 1;
   }
 }
diff --git a/src/tab/selected_tab/_box_shadow.scss b/src/tab/selected_tab/_box_shadow.scss
index 02d5a2c0..a6a66521 100644
--- a/src/tab/selected_tab/_box_shadow.scss
+++ b/src/tab/selected_tab/_box_shadow.scss
@@ -26,7 +26,7 @@ $ucTabBackgroundShadowHard: drop-shadow(-1px 0px 0px var(--uc-tab-shadow-color,
     }
   }
 
-  &[visuallyselected="true"]:not(:focus),
+  &[visuallyselected]:not(:focus),
   &[multiselected]:not([visuallyselected]) {
     //  Original: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9))
     //    Bright: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */
@@ -40,7 +40,7 @@ $ucTabBackgroundShadowHard: drop-shadow(-1px 0px 0px var(--uc-tab-shadow-color,
 :root:not([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(240, 240, 244); --lwt-text-color: rgba(21, 20, 26);"])
   #TabsToolbar:not([brighttext])
   #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+  .tabbrowser-tab:is([visuallyselected], [multiselected])
   > .tab-stack
   > .tab-background:-moz-lwtheme {
   --uc-tab-shadow-color: var(--uc-tab-shadow-color-bundle);
@@ -51,7 +51,7 @@ $ucTabBackgroundShadowHard: drop-shadow(-1px 0px 0px var(--uc-tab-shadow-color,
 :root:not([lwtheme-mozlightdark], [style*="--lwt-accent-color: rgb(28, 27, 34); --lwt-text-color: rgba(251, 251, 254);"])
   #TabsToolbar[brighttext]
   #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+  .tabbrowser-tab:is([visuallyselected], [multiselected])
   > .tab-stack
   > .tab-background:-moz-lwtheme {
   filter: $ucTabBackgroundShadowHard;
diff --git a/src/tab/selected_tab/_photon_like_contextline.scss b/src/tab/selected_tab/_photon_like_contextline.scss
index c98878d2..0b5d4531 100644
--- a/src/tab/selected_tab/_photon_like_contextline.scss
+++ b/src/tab/selected_tab/_photon_like_contextline.scss
@@ -50,7 +50,7 @@
 /* Remove side's background color border */
 #TabsToolbar[brighttext]
   #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+  .tabbrowser-tab:is([visuallyselected], [multiselected])
   > .tab-stack
   > .tab-background:-moz-lwtheme {
   --tabs-border-color: rgba(0, 0, 0, 0.3) !important;
@@ -58,7 +58,7 @@
 }
 #TabsToolbar:not([brighttext])
   #tabbrowser-tabs:not([noshadowfortests])
-  .tabbrowser-tab:is([visuallyselected="true"], [multiselected])
+  .tabbrowser-tab:is([visuallyselected], [multiselected])
   > .tab-stack
   > .tab-background {
   box-shadow: 0 0 1px var(--tabs-border-color), 0 0 4px rgba(128, 128, 142, 0.5) !important; /* Original: 0 0 1px var(--tab-line-color, rgba(128,128,142,0.9)), 0 0 4px rgba(128,128,142,0.5) */