--- a/browser/base/content/contentSearchUI.css
+++ b/browser/base/content/contentSearchUI.css
@@ -9,17 +9,17 @@
   box-shadow: 0 5px 10px hsla(0, 0%, 0%, .1);
   position: absolute;
   left: 0;
   z-index: 1001;
   -moz-user-select: none;
   cursor: default;
 }
 
-.contentSearchSuggestionTable:-moz-dir(rtl) {
+.contentSearchSuggestionTable:dir(rtl) {
   left: auto;
   right: 0;
 }
 
 .contentSearchSuggestionsList {
   border-bottom: 1px solid hsl(0, 0%, 92%);
   width: 100%;
   height: 100%;
@@ -110,17 +110,17 @@
   padding: 0;
   border: none;
   background: none;
   background-image: url('data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAAWCAYAAAABxvaqAAAABmJLR0QA/wD/AP+gvaeTAAAACXBIWXMAAAsTAAALEwEAmpwYAAAAB3RJTUUH3gofECQNNVW2/AAAABBJREFUGFdjOHPmzH8GehEA/KpKg9YTf4AAAAAASUVORK5CYII=');
   background-repeat: no-repeat;
   background-position: right center;
 }
 
-.contentSearchOneOffItem:-moz-dir(rtl) {
+.contentSearchOneOffItem:dir(rtl) {
   background-position: left center;
 }
 
 .contentSearchOneOffItem > img {
   width: 16px;
   height: 16px;
   margin-bottom: -2px;
 }

--- a/browser/themes/shared/searchReset.css
+++ b/browser/themes/shared/searchReset.css
@@ -12,11 +12,11 @@ body {
 
 #defaultEngine {
   padding-inline-start: 26px;
   background-repeat: no-repeat;
   background-position: 5px center;
   background-size: 16px, 16px;
 }
 
-#defaultEngine:-moz-dir(rtl) {
+#defaultEngine:dir(rtl) {
   background-position: calc(100% - 5px) center;
 }

--- a/toolkit/components/aboutperformance/content/aboutPerformance.xhtml
+++ b/toolkit/components/aboutperformance/content/aboutPerformance.xhtml
@@ -111,17 +111,17 @@
         border: 1px solid var(--in-content-border-color);
         border-spacing: 0px;
         float: right;
         margin-bottom: 20px;
         -moz-margin-start: 20px;
         -moz-margin-end: 0;
         width: 100%;
       }
-      #subprocess-reports:-moz-dir(rtl) {
+      #subprocess-reports:dir(rtl) {
         float: left;
       }
       #subprocess-reports th,
       #subprocess-reports td {
         border: 1px solid var(--in-content-border-color);
         padding: 4px;
       }
       #subprocess-reports thead th {