diff --git a/chrome/global/colors.css b/chrome/global/colors.css
index a2e679e..7730316 100644
--- a/chrome/global/colors.css
+++ b/chrome/global/colors.css
@@ -2,7 +2,7 @@
  * https://github.com/bmFtZQ/edge-frfox */
 
 /* default colours (light & dark) */
-:root:not(:-moz-lwtheme),
+:root:not([lwtheme]),
 /* `--newtab-background-color-secondary used` to differentiate between a dark
  * private window and private window with the 'Dark' theme enabled.
  * May not be the most reliable method, but works for now up to FF 123. */
@@ -122,7 +122,7 @@
 }
 
 /* Apply colours to the default 'Auto' theme. */
-#navigator-toolbox:not(:-moz-lwtheme) {
+:root:not([lwtheme]) #navigator-toolbox {
   background-color: var(--lwt-accent-color) !important;
   color: var(--lwt-text-color) !important;
 
@@ -140,7 +140,7 @@
 }
 
 /* Make the titlebar buttons black/white on default themes */
-:root:not(:-moz-lwtheme)[tabsintitlebar] .titlebar-buttonbox {
+:root:not([lwtheme])[tabsintitlebar] .titlebar-buttonbox {
   color: var(--lwt-text-color) !important;
 }
 
@@ -173,7 +173,7 @@
   /* Use accent colour in titlebar when Windows option is enabled. */
   @media (-moz-windows-accent-color-in-titlebar) and (-moz-bool-pref: "browser.theme.windows.accent-color-in-tabs.enabled") {
     /* Uses :root:root to beat specificity of floating tabs adjustments. */
-    :root:root:not(:-moz-lwtheme) {
+    :root:root:not([lwtheme]) {
       --lwt-accent-color: ActiveCaption !important;
       --lwt-text-color: CaptionText !important;
       --lwt-accent-color-inactive: InActiveCaption !important;
@@ -276,7 +276,7 @@
 
 /* Linux / GTK csd support */
 @media (-moz-gtk-csd-available) {
-  :root:not(:-moz-lwtheme),
+  :root:not([lwtheme]),
   /* `--newtab-background-color-secondary used` to differentiate between a dark
    * private window and private window with the 'Dark' theme enabled.
    * May not be the most reliable method, but works for now up to FF 123. */
diff --git a/chrome/global/tweaks.css b/chrome/global/tweaks.css
index 38ba859..b1010af 100644
--- a/chrome/global/tweaks.css
+++ b/chrome/global/tweaks.css
@@ -10,7 +10,7 @@
 /* force tabs to toolbar bg (useful for proton themes) (might experience some
 bugs with certain themes eg. dark text on dark background.) */
 @media (-moz-bool-pref: "uc.tweak.force-tab-colour") {
-  :root:-moz-lwtheme {
+  :root[lwtheme] {
     --tab-selected-bgcolor: var(--toolbar-bgcolor) !important;
     --tab-selected-textcolor: var(--toolbar-color) !important;
   }
@@ -27,7 +27,7 @@ bugs with certain themes eg. dark text on dark background.) */
 }
 
 @media (-moz-bool-pref: "uc.tweak.floating-tabs") {
-  :root:not(:-moz-lwtheme),
+  :root:not([lwtheme]),
   /* `--newtab-background-color-secondary used` to differentiate between a dark
    * private window and private window with the 'Dark' theme enabled.
    * May not be the most reliable method, but works for now up to FF 123. */
@@ -54,7 +54,7 @@ bugs with certain themes eg. dark text on dark background.) */
   }
 
   @media (-moz-gtk-csd-available) {
-    :root:not(:-moz-lwtheme) {
+    :root:not([lwtheme]) {
       --toolbar-bgcolor: color-mix(in srgb, -moz-dialog 80%, #fff) !important;
       --toolbar-field-background-color: Field !important;
       --lwt-tab-text: -moz-dialogtext !important;
diff --git a/chrome/toolbar/findbar.css b/chrome/toolbar/findbar.css
index 74d7de9..a043810 100644
--- a/chrome/toolbar/findbar.css
+++ b/chrome/toolbar/findbar.css
@@ -8,7 +8,7 @@
   background-color: var(--toolbar-field-background-color) !important;
 
   /* Add shadow when in light mode with no theme applied, like the URL bar. */
-  &:not(:-moz-lwtheme) {
+  :root:not([lwtheme]) & {
     box-shadow: 0 0 4px light-dark(rgb(0 0 0 / .1), transparent) !important;
   }
 
diff --git a/chrome/toolbar/urlbar.css b/chrome/toolbar/urlbar.css
index 1b1f852..9333dbe 100644
--- a/chrome/toolbar/urlbar.css
+++ b/chrome/toolbar/urlbar.css
@@ -38,7 +38,7 @@
   border-radius: calc(var(--urlbar-icon-border-radius) + 2px) !important;
 
   /* Shadow for URL bar, only appears in light mode. */
-  :root:not(:-moz-lwtheme) #nav-bar:not([brighttext]) & {
+  :root:not([lwtheme]) #nav-bar:not([brighttext]) & {
     box-shadow: var(--uc-urlbar-shadow, none);
   }
 
@@ -49,7 +49,7 @@
     box-shadow: 0 10px 16px rgb(0 0 0 / 0.18), 0 3px 5px rgb(0 0 0 / 0.33) !important;
     outline: 0.5px solid var(--arrowpanel-border-color) !important;
 
-    &:not(:-moz-lwtheme) {
+    :root:not([lwtheme]) & {
       outline-color: var(--panel-separator-color) !important;
     }
   }
@@ -128,7 +128,7 @@
 
 /* Search engine indicator. */
 #urlbar-search-mode-indicator {
-  :root:not(:-moz-lwtheme) & {
+  :root:not([lwtheme]) & {
     background-color: var(--urlbar-box-hover-bgcolor) !important;
   }