diff --git a/browser/components/preferences/in-content/main.js b/browser/components/preferences/in-content/main.js
index e6605011e4e..fefff1c53ab 100644
--- a/browser/components/preferences/in-content/main.js
+++ b/browser/components/preferences/in-content/main.js
@@ -97,6 +97,19 @@ var gMainPane = {
     e10sCheckbox.checked = e10sPref.value || e10sTempPref.value;
 #endif
 
+#ifdef MOZ_DEV_EDITION
+    Cu.import("resource://gre/modules/osfile.jsm");
+    let uAppData = OS.Constants.Path.userApplicationDataDir;
+    let ignoreSeparateProfile = OS.Path.join(uAppData, "ignore-dev-edition-profile");
+
+    setEventListener("separateProfileMode", "command", gMainPane.separateProfileModeChange);
+    let separateProfileModeCheckbox = document.getElementById("separateProfileMode");
+    setEventListener("getStarted", "click", gMainPane.onGetStarted);
+
+    OS.File.stat(ignoreSeparateProfile).then(() => separateProfileModeCheckbox.checked = false,
+                                             () => separateProfileModeCheckbox.checked = true);
+#endif
+
     // Notify observers that the UI is now ready
     Components.classes["@mozilla.org/observer-service;1"]
               .getService(Components.interfaces.nsIObserverService)
@@ -154,6 +167,66 @@ var gMainPane = {
   },
 #endif
 
+#ifdef MOZ_DEV_EDITION
+  separateProfileModeChange: function ()
+  {
+    function quitApp() {
+      Services.startup.quit(Ci.nsIAppStartup.eAttemptQuit |  Ci.nsIAppStartup.eRestart);
+    }
+    function revertCheckbox(error) {
+      separateProfileModeCheckbox.checked = !separateProfileModeCheckbox.checked;
+      if (error) {
+        Cu.reportError("Failed to toggle separate profile mode: " + error);
+      }
+    }
+
+    const Cc = Components.classes, Ci = Components.interfaces;
+    let separateProfileModeCheckbox = document.getElementById("separateProfileMode");
+    let brandName = document.getElementById("bundleBrand").getString("brandShortName");
+    let bundle = document.getElementById("bundlePreferences");
+    let msg = bundle.getFormattedString(separateProfileModeCheckbox.checked ?
+                                        "featureEnableRequiresRestart" : "featureDisableRequiresRestart",
+                                        [brandName]);
+    let title = bundle.getFormattedString("shouldRestartTitle", [brandName]);
+    let shouldProceed = Services.prompt.confirm(window, title, msg)
+    if (shouldProceed) {
+      let cancelQuit = Cc["@mozilla.org/supports-PRBool;1"]
+                         .createInstance(Ci.nsISupportsPRBool);
+      Services.obs.notifyObservers(cancelQuit, "quit-application-requested",
+                                   "restart");
+      shouldProceed = !cancelQuit.data;
+
+      if (shouldProceed) {
+        Cu.import("resource://gre/modules/osfile.jsm");
+        let uAppData = OS.Constants.Path.userApplicationDataDir;
+        let ignoreSeparateProfile = OS.Path.join(uAppData, "ignore-dev-edition-profile");
+
+        if (separateProfileModeCheckbox.checked) {
+          OS.File.remove(ignoreSeparateProfile).then(quitApp, revertCheckbox);
+        } else {
+          OS.File.writeAtomic(ignoreSeparateProfile, new Uint8Array()).then(quitApp, revertCheckbox);
+        }
+        return;
+      }
+    }
+
+    // Revert the checkbox in case we didn't quit
+    revertCheckbox();
+  },
+
+  onGetStarted: function (aEvent) {
+    const Cc = Components.classes, Ci = Components.interfaces;
+    let wm = Cc["@mozilla.org/appshell/window-mediator;1"]
+                .getService(Ci.nsIWindowMediator);
+    let win = wm.getMostRecentWindow("navigator:browser");
+
+    if (win) {
+      let accountsTab = win.gBrowser.addTab("about:accounts?action=migrateToDevEdition");
+      win.gBrowser.selectedTab = accountsTab;
+    }
+  },
+#endif
+
   // HOME PAGE
 
   /*
diff --git a/browser/components/preferences/in-content/main.xul b/browser/components/preferences/in-content/main.xul
index 78c4416fefb..c9c57e73590 100644
--- a/browser/components/preferences/in-content/main.xul
+++ b/browser/components/preferences/in-content/main.xul
@@ -117,6 +117,17 @@
           hidden="true">
   <caption><label>&startup.label;</label></caption>
 
+#ifdef MOZ_DEV_EDITION
+  <vbox id="separateProfileBox">
+    <checkbox id="separateProfileMode"
+              label="&separateProfileMode.label;"/>
+    <hbox align="center" class="indent">
+      <label id="useFirefoxSync">&useFirefoxSync.label;</label>
+      <label id="getStarted" class="text-link">&getStarted.label;</label>
+    </hbox>
+  </vbox>
+#endif
+
 #ifdef E10S_TESTING_ONLY
   <checkbox id="e10sAutoStart"
             label="Enable E10S (multi-process)"/>
@@ -126,13 +137,13 @@
   <vbox id="defaultBrowserBox">
     <hbox align="center">
       <checkbox id="alwaysCheckDefault" preference="browser.shell.checkDefaultBrowser"
-                label="&alwaysCheckDefault.label;" accesskey="&alwaysCheckDefault2.accesskey;"/>
+                label="&alwaysCheckDefault2.label;" accesskey="&alwaysCheckDefault2.accesskey;"/>
     </hbox>
     <deck id="setDefaultPane">
       <hbox align="center" class="indent">
         <label id="isNotDefaultLabel" flex="1">&isNotDefault.label;</label>
         <button id="setDefaultButton"
-                label="&setAsMyDefaultBrowser.label;" accesskey="&setAsMyDefaultBrowser.accesskey;"
+                label="&setAsMyDefaultBrowser2.label;" accesskey="&setAsMyDefaultBrowser2.accesskey;"
                 preference="pref.general.disable_button.default_browser"/>
       </hbox>
       <hbox align="center" class="indent">
diff --git a/browser/components/preferences/main.js b/browser/components/preferences/main.js
index 937479948dc..e8c46692e10 100644
--- a/browser/components/preferences/main.js
+++ b/browser/components/preferences/main.js
@@ -60,12 +60,87 @@ var gMainPane = {
 
     this.updateBrowserStartupLastSession();
 
+#ifdef MOZ_DEV_EDITION
+    let separateProfileModeCheckbox = document.getElementById("separateProfileMode");
+    let listener = gMainPane.separateProfileModeChange.bind(gMainPane);
+    separateProfileModeCheckbox.addEventListener("command", listener);
+
+    let getStartedLink = document.getElementById("getStarted");
+    let syncListener = gMainPane.onGetStarted.bind(gMainPane);
+    getStartedLink.addEventListener("click", syncListener);
+
+    Cu.import("resource://gre/modules/osfile.jsm");
+    let uAppData = OS.Constants.Path.userApplicationDataDir;
+    let ignoreSeparateProfile = OS.Path.join(uAppData, "ignore-dev-edition-profile");
+
+    OS.File.stat(ignoreSeparateProfile).then(() => separateProfileModeCheckbox.checked = false,
+                                             () => separateProfileModeCheckbox.checked = true);
+#endif
+
     // Notify observers that the UI is now ready
     Components.classes["@mozilla.org/observer-service;1"]
               .getService(Components.interfaces.nsIObserverService)
               .notifyObservers(window, "main-pane-loaded", null);
   },
 
+#ifdef MOZ_DEV_EDITION
+  separateProfileModeChange: function ()
+  {
+    function quitApp() {
+      Services.startup.quit(Ci.nsIAppStartup.eAttemptQuit |  Ci.nsIAppStartup.eRestart);
+    }
+    function revertCheckbox(error) {
+      separateProfileModeCheckbox.checked = !separateProfileModeCheckbox.checked;
+      if (error) {
+        Cu.reportError("Failed to toggle separate profile mode: " + error);
+      }
+    }
+
+    let separateProfileModeCheckbox = document.getElementById("separateProfileMode");
+    let brandName = document.getElementById("bundleBrand").getString("brandShortName");
+    let bundle = document.getElementById("bundlePreferences");
+    let msg = bundle.getFormattedString(separateProfileModeCheckbox.checked ?
+                                        "featureEnableRequiresRestart" : "featureDisableRequiresRestart",
+                                        [brandName]);
+    let title = bundle.getFormattedString("shouldRestartTitle", [brandName]);
+    let shouldProceed = Services.prompt.confirm(window, title, msg)
+    if (shouldProceed) {
+      let cancelQuit = Cc["@mozilla.org/supports-PRBool;1"]
+                         .createInstance(Ci.nsISupportsPRBool);
+      Services.obs.notifyObservers(cancelQuit, "quit-application-requested",
+                                   "restart");
+      shouldProceed = !cancelQuit.data;
+
+      if (shouldProceed) {
+        Cu.import("resource://gre/modules/osfile.jsm");
+        let uAppData = OS.Constants.Path.userApplicationDataDir;
+        let ignoreSeparateProfile = OS.Path.join(uAppData, "ignore-dev-edition-profile");
+
+        if (separateProfileModeCheckbox.checked) {
+          OS.File.remove(ignoreSeparateProfile).then(quitApp, revertCheckbox);
+        } else {
+          OS.File.writeAtomic(ignoreSeparateProfile, new Uint8Array()).then(quitApp, revertCheckbox);
+        }
+      }
+    }
+
+    // Revert the checkbox in case we didn't quit
+    revertCheckbox();
+  },
+
+  onGetStarted: function (aEvent) {
+    const Cc = Components.classes, Ci = Components.interfaces;
+    let wm = Cc["@mozilla.org/appshell/window-mediator;1"]
+               .getService(Ci.nsIWindowMediator);
+    let win = wm.getMostRecentWindow("navigator:browser");
+
+    if (win) {
+      let accountsTab = win.gBrowser.addTab("about:accounts?action=migrateToDevEdition");
+      win.gBrowser.selectedTab = accountsTab;
+    }
+  },
+#endif
+
   // HOME PAGE
 
   /*
diff --git a/browser/components/preferences/main.xul b/browser/components/preferences/main.xul
index 8c27b8c8848..cd5d4508a96 100644
--- a/browser/components/preferences/main.xul
+++ b/browser/components/preferences/main.xul
@@ -77,17 +77,28 @@
     <groupbox id="startupGroup">
       <caption label="&startup.label;"/>
 
+#ifdef MOZ_DEV_EDITION
+      <vbox id="separateProfileBox">
+        <checkbox id="separateProfileMode"
+                  label="&separateProfileMode.label;"/>
+        <hbox align="center" class="indent">
+          <label id="useFirefoxSync">&useFirefoxSync.label;</label>
+          <label id="getStarted" class="text-link">&getStarted.label;</label>
+        </hbox>
+      </vbox>
+#endif
+
 #ifdef HAVE_SHELL_SERVICE
       <vbox id="defaultBrowserBox">
         <hbox align="center">
           <checkbox id="alwaysCheckDefault" preference="browser.shell.checkDefaultBrowser"
-                    label="&alwaysCheckDefault.label;" accesskey="&alwaysCheckDefault2.accesskey;"/>
+                    label="&alwaysCheckDefault2.label;" accesskey="&alwaysCheckDefault2.accesskey;"/>
         </hbox>
         <deck id="setDefaultPane">
           <hbox align="center" class="indent">
             <label id="isNotDefaultLabel" flex="1">&isNotDefault.label;</label>
             <button id="setDefaultButton"
-                    label="&setAsMyDefaultBrowser.label;" accesskey="&setAsMyDefaultBrowser.accesskey;"
+                    label="&setAsMyDefaultBrowser2.label;" accesskey="&setAsMyDefaultBrowser2.accesskey;"
                     oncommand="gMainPane.setDefaultBrowser();"
                     preference="pref.general.disable_button.default_browser"/>
           </hbox>
diff --git a/browser/locales/en-US/chrome/browser/preferences/main.dtd b/browser/locales/en-US/chrome/browser/preferences/main.dtd
index 2951b15dc36..95a44981fc7 100644
--- a/browser/locales/en-US/chrome/browser/preferences/main.dtd
+++ b/browser/locales/en-US/chrome/browser/preferences/main.dtd
@@ -31,10 +31,13 @@
 <!ENTITY alwaysAsk.label "Always ask me where to save files">
 <!ENTITY alwaysAsk.accesskey "A">
 
-<!ENTITY alwaysCheckDefault.label         "Always check to see if &brandShortName; is the default browser on startup">
+<!ENTITY alwaysCheckDefault2.label        "Always check if &brandShortName; is your default browser">
 <!ENTITY alwaysCheckDefault2.accesskey    "w">
-<!ENTITY setAsMyDefaultBrowser.label      "Make &brandShortName; My Default Browser">
-<!ENTITY setAsMyDefaultBrowser.accesskey  "D">
+<!ENTITY setAsMyDefaultBrowser2.label     "Make Default">
+<!ENTITY setAsMyDefaultBrowser2.accesskey "D">
 <!ENTITY isDefault.label                  "&brandShortName; is currently your default browser">
 <!ENTITY isNotDefault.label               "&brandShortName; is not your default browser">
 
+<!ENTITY separateProfileMode.label        "Allow &brandShortName; and Firefox to run at the same time">
+<!ENTITY useFirefoxSync.label             "Tip: This uses separate profiles. Use Sync to share data between them.">
+<!ENTITY getStarted.label                 "Start using Sync…">
diff --git a/browser/themes/linux/preferences/preferences.css b/browser/themes/linux/preferences/preferences.css
index f0565f955cf..947a5407c70 100644
--- a/browser/themes/linux/preferences/preferences.css
+++ b/browser/themes/linux/preferences/preferences.css
@@ -55,6 +55,11 @@ label.small {
 }
 
 /* General Pane */
+#useFirefoxSync,
+#getStarted {
+  font-size: 90%;
+}
+
 #isNotDefaultLabel {
   font-weight: bold;
 }
diff --git a/browser/themes/osx/preferences/preferences.css b/browser/themes/osx/preferences/preferences.css
index 06d418f3c35..ffaf8de103a 100644
--- a/browser/themes/osx/preferences/preferences.css
+++ b/browser/themes/osx/preferences/preferences.css
@@ -169,6 +169,11 @@ caption {
 
 /* General Pane */
 
+#useFirefoxSync,
+#getStarted {
+  font-size: 90%;
+}
+
 #isNotDefaultLabel {
   font-weight: bold;
 }
diff --git a/browser/themes/shared/incontentprefs/preferences.css b/browser/themes/shared/incontentprefs/preferences.css
index ce284b6039f..644589605bd 100644
--- a/browser/themes/shared/incontentprefs/preferences.css
+++ b/browser/themes/shared/incontentprefs/preferences.css
@@ -110,6 +110,15 @@ treecol {
 
 /* General Pane */
 
+#useFirefoxSync  {
+  font-size: 90%;
+  -moz-margin-end: 8px !important;
+}
+
+#getStarted {
+  font-size: 90%;
+}
+
 #isNotDefaultLabel {
   font-weight: bold;
 }
diff --git a/browser/themes/windows/preferences/preferences.css b/browser/themes/windows/preferences/preferences.css
index 1aa2deaa3b0..f63a5613e1a 100644
--- a/browser/themes/windows/preferences/preferences.css
+++ b/browser/themes/windows/preferences/preferences.css
@@ -55,6 +55,11 @@ label.small {
 
 /* General Pane */
 
+#useFirefoxSync,
+#getStarted {
+  font-size: 90%;
+}
+
 #isNotDefaultLabel {
   font-weight: bold;
 }
diff --git a/toolkit/profile/nsIToolkitProfileService.idl b/toolkit/profile/nsIToolkitProfileService.idl
index 316e8b05f77..bc0606ca1fe 100644
--- a/toolkit/profile/nsIToolkitProfileService.idl
+++ b/toolkit/profile/nsIToolkitProfileService.idl
@@ -29,6 +29,12 @@ interface nsIToolkitProfileService : nsISupports
      * browser if no other profile is specified at runtime). This is the profile
      * marked with Default=1 in profiles.ini and is usually the same as
      * selectedProfile, except on Developer Edition.
+     *
+     * Developer Edition uses a profile named "dev-edition-default" as the
+     * default profile (which it creates if it doesn't exist), unless a special
+     * empty file named "ignore-dev-edition-profile" is present next to
+     * profiles.ini. In that case Developer Edition behaves the same as any
+     * other build of Firefox.
      */
     attribute nsIToolkitProfile defaultProfile;
 
diff --git a/toolkit/profile/nsToolkitProfileService.cpp b/toolkit/profile/nsToolkitProfileService.cpp
index f6afd4a9989..47fb53ccdd1 100644
--- a/toolkit/profile/nsToolkitProfileService.cpp
+++ b/toolkit/profile/nsToolkitProfileService.cpp
@@ -424,6 +424,22 @@ nsToolkitProfileService::Init()
 
     nsToolkitProfile* currentProfile = nullptr;
 
+#ifdef MOZ_DEV_EDITION
+    nsCOMPtr<nsIFile> ignoreSeparateProfile;
+    rv = mAppData->Clone(getter_AddRefs(ignoreSeparateProfile));
+    if (NS_FAILED(rv))
+        return rv;
+
+    rv = ignoreSeparateProfile->AppendNative(NS_LITERAL_CSTRING("ignore-dev-edition-profile"));
+    if (NS_FAILED(rv))
+        return rv;
+
+    bool shouldIgnoreSeparateProfile;
+    rv = ignoreSeparateProfile->Exists(&shouldIgnoreSeparateProfile);
+    if (NS_FAILED(rv))
+        return rv;
+#endif
+
     unsigned int c = 0;
     bool foundAuroraDefault = false;
     for (c = 0; true; ++c) {
@@ -485,8 +501,9 @@ nsToolkitProfileService::Init()
             this->SetDefaultProfile(currentProfile);
         }
 #ifdef MOZ_DEV_EDITION
-        // Use the dev-edition-default profile if this is an Aurora build.
-        if (name.EqualsLiteral("dev-edition-default")) {
+        // Use the dev-edition-default profile if this is an Aurora build and
+        // ignore-dev-edition-profile is not present.
+        if (name.EqualsLiteral("dev-edition-default") && !shouldIgnoreSeparateProfile) {
             mChosen = currentProfile;
             foundAuroraDefault = true;
         }
@@ -498,7 +515,7 @@ nsToolkitProfileService::Init()
     // on webapprt.
     bool isFirefox = strcmp(gAppData->ID,
                             "{ec8030f7-c20a-464f-9b0e-13a3a9e97384}") == 0;
-    if (!foundAuroraDefault && isFirefox) {
+    if (!foundAuroraDefault && isFirefox && !shouldIgnoreSeparateProfile) {
         // If a single profile exists, it may not be already marked as default.
         // Do it now to avoid problems when we create the dev-edition-default profile.
         if (!mChosen && mFirst && !mFirst->mNext)