diff --git a/caps/nsIScriptSecurityManager.idl b/caps/nsIScriptSecurityManager.idl
index ccf8a8fa747b..8b44a2885c92 100644
--- a/caps/nsIScriptSecurityManager.idl
+++ b/caps/nsIScriptSecurityManager.idl
@@ -246,9 +246,6 @@ interface nsIScriptSecurityManager : nsISupports
      */
     nsIPrincipal getChannelURIPrincipal(in nsIChannel aChannel);
 
-    const unsigned long NO_APP_ID = 0;
-    const unsigned long UNKNOWN_APP_ID = 4294967295; // UINT32_MAX
-
     const unsigned long DEFAULT_USER_CONTEXT_ID = 0;
 
     /**
diff --git a/caps/tests/unit/test_origin.js b/caps/tests/unit/test_origin.js
index 48912bfc8395..e2b2a06cb1af 100644
--- a/caps/tests/unit/test_origin.js
+++ b/caps/tests/unit/test_origin.js
@@ -103,20 +103,6 @@ function run_test() {
   checkOriginAttributes(exampleOrg_firstPartyDomain, { firstPartyDomain: "example.org" }, "^firstPartyDomain=example.org");
   Assert.equal(exampleOrg_firstPartyDomain.origin, "http://example.org^firstPartyDomain=example.org");
 
-  // Make sure we don't crash when serializing principals with UNKNOWN_APP_ID.
-  try {
-    let binaryStream = Cc["@mozilla.org/binaryoutputstream;1"].
-                       createInstance(Ci.nsIObjectOutputStream);
-    let pipe = Cc["@mozilla.org/pipe;1"].createInstance(Ci.nsIPipe);
-    pipe.init(false, false, 0, 0xffffffff, null);
-    binaryStream.setOutputStream(pipe.outputStream);
-    binaryStream.writeCompoundObject(simplePrin, Ci.nsISupports, true); // eslint-disable-line no-undef
-    binaryStream.close();
-  } catch (e) {
-    Assert.ok(true);
-  }
-
-
   // Just userContext.
   var exampleOrg_userContext = ssm.createCodebasePrincipal(makeURI("http://example.org"), {userContextId: 42});
   checkOriginAttributes(exampleOrg_userContext, { userContextId: 42 }, "^userContextId=42");
diff --git a/dom/ipc/PTabContext.ipdlh b/dom/ipc/PTabContext.ipdlh
index f0e64e85f7db..97e926f1c4b8 100644
--- a/dom/ipc/PTabContext.ipdlh
+++ b/dom/ipc/PTabContext.ipdlh
@@ -20,8 +20,7 @@ namespace dom {
 //
 // If isMozBrowserElement is false, this PopupIPCTabContext is either a
 // <xul:browser> or an app frame.  The frame's app-id and app-frame-owner-app-id
-// will be equal to the opener's values.  For a <xul:browser>, those app IDs
-// will be NO_APP_ID.
+// will be equal to the opener's values.
 //
 // It's an error to set isMozBrowserElement == false if opener is a mozbrowser
 // element.  Such a PopupIPCTabContext should be rejected by code which receives
diff --git a/dom/ipc/TabContext.cpp b/dom/ipc/TabContext.cpp
index 66779fcfd499..ced3e37caf77 100644
--- a/dom/ipc/TabContext.cpp
+++ b/dom/ipc/TabContext.cpp
@@ -12,8 +12,6 @@
 #include "nsIScriptSecurityManager.h"
 #include "nsServiceManagerUtils.h"
 
-#define NO_APP_ID (nsIScriptSecurityManager::NO_APP_ID)
-
 using namespace mozilla::dom::ipc;
 using namespace mozilla::layout;
 
diff --git a/dom/quota/ActorsParent.cpp b/dom/quota/ActorsParent.cpp
index 0da5890162c3..30eaaa4d0110 100644
--- a/dom/quota/ActorsParent.cpp
+++ b/dom/quota/ActorsParent.cpp
@@ -2034,7 +2034,7 @@ void GetJarPrefix(bool aInIsolatedMozBrowser, nsACString& aJarPrefix) {
   // AppId is an unused b2g identifier. Let's set it to 0 all the time (see bug
   // 1320404).
   // aJarPrefix = appId + "+" + { 't', 'f' } + "+";
-  aJarPrefix.AppendInt(nsIScriptSecurityManager::NO_APP_ID);
+  aJarPrefix.AppendInt(0);  // TODO: this is the appId, to be removed.
   aJarPrefix.Append('+');
   aJarPrefix.Append(aInIsolatedMozBrowser ? 't' : 'f');
   aJarPrefix.Append('+');
diff --git a/dom/storage/StorageUtils.cpp b/dom/storage/StorageUtils.cpp
index 03a2a150dc49..283fbb1852c7 100644
--- a/dom/storage/StorageUtils.cpp
+++ b/dom/storage/StorageUtils.cpp
@@ -119,7 +119,7 @@ nsCString Scheme0Scope(const nsACString& aOriginSuffix,
   }
 
   if (oa.mInIsolatedMozBrowser) {
-    result.AppendInt(nsIScriptSecurityManager::NO_APP_ID);
+    result.AppendInt(0);  // This is the appId to be removed.
     result.Append(':');
     result.Append(oa.mInIsolatedMozBrowser ? 't' : 'f');
     result.Append(':');
diff --git a/mobile/android/components/ContentPermissionPrompt.js b/mobile/android/components/ContentPermissionPrompt.js
index 07b2fa5e9935..0a740053fcf9 100644
--- a/mobile/android/components/ContentPermissionPrompt.js
+++ b/mobile/android/components/ContentPermissionPrompt.js
@@ -24,7 +24,7 @@ ContentPermissionPrompt.prototype = {
 
   QueryInterface: ChromeUtils.generateQI([Ci.nsIContentPermissionPrompt]),
 
-  handleExistingPermission: function handleExistingPermission(request, type, isApp, callback) {
+  handleExistingPermission: function handleExistingPermission(request, type, callback) {
     let result = Services.perms.testExactPermissionFromPrincipal(request.principal, type);
     if (result == Ci.nsIPermissionManager.ALLOW_ACTION) {
       callback(/* allow */ true);
@@ -36,11 +36,6 @@ ContentPermissionPrompt.prototype = {
       return true;
     }
 
-    if (isApp && result == Ci.nsIPermissionManager.UNKNOWN_ACTION) {
-      callback(/* allow */ false);
-      return true;
-    }
-
     return false;
   },
 
@@ -59,8 +54,6 @@ ContentPermissionPrompt.prototype = {
   },
 
   prompt: function(request) {
-    let isApp = request.principal.appId !== Ci.nsIScriptSecurityManager.NO_APP_ID && request.principal.appId !== Ci.nsIScriptSecurityManager.UNKNOWN_APP_ID;
-
     // Only allow exactly one permission rquest here.
     let types = request.types.QueryInterface(Ci.nsIArray);
     if (types.length != 1) {
@@ -86,7 +79,7 @@ ContentPermissionPrompt.prototype = {
     };
 
     // Returns true if the request was handled
-    if (this.handleExistingPermission(request, perm.type, isApp, callback)) {
+    if (this.handleExistingPermission(request, perm.type, callback)) {
        return;
     }
 
@@ -116,9 +109,6 @@ ContentPermissionPrompt.prototype = {
         // If the user checked "Don't ask again" or this is a desktopNotification, make a permanent exception
         if (aChecked || entityName == "desktopNotification2") {
           Services.perms.addFromPrincipal(request.principal, perm.type, Ci.nsIPermissionManager.ALLOW_ACTION);
-        } else if (isApp) {
-          // Otherwise allow the permission for the current session if the request comes from an app
-          Services.perms.addFromPrincipal(request.principal, perm.type, Ci.nsIPermissionManager.ALLOW_ACTION, Ci.nsIPermissionManager.EXPIRE_SESSION);
         }
 
         callback(/* allow */ true);
diff --git a/netwerk/base/nsILoadContextInfo.idl b/netwerk/base/nsILoadContextInfo.idl
index fe59ac08ec64..bbf2b5d48ac5 100644
--- a/netwerk/base/nsILoadContextInfo.idl
+++ b/netwerk/base/nsILoadContextInfo.idl
@@ -23,9 +23,6 @@ interface nsIDOMWindow;
 [scriptable, builtinclass, uuid(555e2f8a-a1f6-41dd-88ca-ed4ed6b98a22)]
 interface nsILoadContextInfo : nsISupports
 {
-  const unsigned long NO_APP_ID = 0;
-  const unsigned long UNKNOWN_APP_ID = 4294967295; // UINT32_MAX
-
   /**
    * Whether the context is in a Private Browsing mode
    */