diff --git a/l10n/en-US/viewer.ftl b/l10n/en-US/viewer.ftl
index 9242a298a2d3f..6bbec786b59e9 100644
--- a/l10n/en-US/viewer.ftl
+++ b/l10n/en-US/viewer.ftl
@@ -58,14 +58,6 @@ pdfjs-bookmark-button =
     .title = Current Page (View URL from Current Page)
 pdfjs-bookmark-button-label = Current Page
 
-# Used in Firefox for Android.
-pdfjs-open-in-app-button =
-    .title = Open in app
-
-# Used in Firefox for Android.
-# Length of the translation matters since we are in a mobile context, with limited screen estate.
-pdfjs-open-in-app-button-label = Open in app
-
 ##  Secondary toolbar and context menu
 
 pdfjs-tools-button =
diff --git a/web/app.js b/web/app.js
index 05a080ee60305..587ffc5bb8e64 100644
--- a/web/app.js
+++ b/web/app.js
@@ -1168,10 +1168,6 @@ const PDFViewerApplication = {
     }
   },
 
-  openInExternalApp() {
-    this.downloadOrSave({ openInExternalApp: true });
-  },
-
   /**
    * Report the error; used for errors affecting loading and/or parsing of
    * the entire PDF document.
@@ -1928,7 +1924,6 @@ const PDFViewerApplication = {
     );
     eventBus._on("print", webViewerPrint);
     eventBus._on("download", webViewerDownload);
-    eventBus._on("openinexternalapp", webViewerOpenInExternalApp);
     eventBus._on("firstpage", webViewerFirstPage);
     eventBus._on("lastpage", webViewerLastPage);
     eventBus._on("nextpage", webViewerNextPage);
@@ -2064,7 +2059,6 @@ const PDFViewerApplication = {
     eventBus._off("presentationmode", webViewerPresentationMode);
     eventBus._off("print", webViewerPrint);
     eventBus._off("download", webViewerDownload);
-    eventBus._off("openinexternalapp", webViewerOpenInExternalApp);
     eventBus._off("firstpage", webViewerFirstPage);
     eventBus._off("lastpage", webViewerLastPage);
     eventBus._off("nextpage", webViewerNextPage);
@@ -2485,9 +2479,6 @@ function webViewerPrint() {
 function webViewerDownload() {
   PDFViewerApplication.downloadOrSave();
 }
-function webViewerOpenInExternalApp() {
-  PDFViewerApplication.openInExternalApp();
-}
 function webViewerFirstPage() {
   PDFViewerApplication.page = 1;
 }
diff --git a/web/images/gv-toolbarButton-openinapp.svg b/web/images/gv-toolbarButton-openinapp.svg
deleted file mode 100644
index 80ec891aad643..0000000000000
--- a/web/images/gv-toolbarButton-openinapp.svg
+++ /dev/null
@@ -1,11 +0,0 @@
-<svg width="24" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg">
-<path d="M4 4.5H6.5V7H4V4.5Z" fill="black"/>
-<path d="M6.5 10.5H4V13H6.5V10.5Z" fill="black"/>
-<path d="M13.25 10.5H10.75V13H13.25V10.5Z" fill="black"/>
-<path d="M17.5 10.5H20V13H17.5V10.5Z" fill="black"/>
-<path d="M6.5 16.5H4V19H6.5V16.5Z" fill="black"/>
-<path d="M10.75 16.5H13.25V19H10.75V16.5Z" fill="black"/>
-<path d="M20 16.5H17.5V19H20V16.5Z" fill="black"/>
-<path d="M13.25 4.5H10.75V7H13.25V4.5Z" fill="black"/>
-<path d="M17.5 4.5H20V7H17.5V4.5Z" fill="black"/>
-</svg>
diff --git a/web/toolbar-geckoview.js b/web/toolbar-geckoview.js
index 0d1ffab047600..70a40b81bf800 100644
--- a/web/toolbar-geckoview.js
+++ b/web/toolbar-geckoview.js
@@ -38,11 +38,6 @@ class Toolbar {
         eventName: "download",
         nimbusName: "download-button",
       },
-      {
-        element: options.openInApp,
-        eventName: "openinexternalapp",
-        nimbusName: "open-in-app-button",
-      },
     ];
 
     if (nimbusData) {
diff --git a/web/viewer-geckoview.css b/web/viewer-geckoview.css
index 28312795ef48c..0ae1a48fbeea5 100644
--- a/web/viewer-geckoview.css
+++ b/web/viewer-geckoview.css
@@ -39,7 +39,6 @@
   --toolbar-fg-color: #15141a;
 
   --toolbarButton-download-icon: url(images/gv-toolbarButton-download.svg);
-  --toolbarButton-openinapp-icon: url(images/gv-toolbarButton-openinapp.svg);
 }
 
 :root:dir(rtl) {
@@ -232,10 +231,6 @@ body {
   mask-image: var(--toolbarButton-download-icon);
 }
 
-#openInApp::before {
-  mask-image: var(--toolbarButton-openinapp-icon);
-}
-
 .dialogButton {
   width: auto;
   margin: 3px 4px 2px !important;
diff --git a/web/viewer-geckoview.html b/web/viewer-geckoview.html
index 16387bba63e3e..7d0d936f74e18 100644
--- a/web/viewer-geckoview.html
+++ b/web/viewer-geckoview.html
@@ -95,9 +95,6 @@
           <button id="download" class="toolbarButton" title="Download" tabindex="31" data-l10n-id="pdfjs-download-button">
             <span data-l10n-id="pdfjs-download-button-label">Download</span>
           </button>
-          <button id="openInApp" class="toolbarButton" title="Open in app" tabindex="32" data-l10n-id="pdfjs-open-in-app-button">
-            <span data-l10n-id="pdfjs-open-in-app-button-label">Open in app</span>
-          </button>
         </div>
 
         <div id="viewerContainer" tabindex="0">
diff --git a/web/viewer-geckoview.js b/web/viewer-geckoview.js
index 31694567a8e3e..962eddd763d00 100644
--- a/web/viewer-geckoview.js
+++ b/web/viewer-geckoview.js
@@ -44,7 +44,6 @@ function getViewerConfiguration() {
       mainContainer,
       container: document.getElementById("floatingToolbar"),
       download: document.getElementById("download"),
-      openInApp: document.getElementById("openInApp"),
     },
 
     passwordOverlay: {