diff --git a/install.rdf b/install.rdf
index cd4516c..8ead37f 100644
--- a/install.rdf
+++ b/install.rdf
@@ -16,7 +16,7 @@
         <em:maxVersion>*</em:maxVersion>
       </Description>
     </em:targetApplication>
-    <em:version>3.1.1</em:version>
+    <em:version>4.0.0</em:version>
     <em:unpack>false</em:unpack>
   </Description>
 </RDF>
diff --git a/package.json b/package.json
index a87e30c..00f389e 100644
--- a/package.json
+++ b/package.json
@@ -2,7 +2,7 @@
   "name": "testpilot-containers",
   "title": "Firefox Multi-Account Containers",
   "description": "Containers helps you keep all the parts of your online life contained in different tabs. Custom labels and color-coded tabs help keep different activities — like online shopping, travel planning, or checking work email — separate.",
-  "version": "3.1.1",
+  "version": "4.0.0",
   "author": "Andrea Marchesini, Luke Crouch and Jonathan Kingston",
   "bugs": {
     "url": "https://github.com/mozilla/testpilot-containers/issues"
diff --git a/webextension/manifest.json b/webextension/manifest.json
index 0d601f7..3c60383 100644
--- a/webextension/manifest.json
+++ b/webextension/manifest.json
@@ -1,7 +1,7 @@
 {
   "manifest_version": 2,
   "name": "Firefox Multi-Account Containers",
-  "version": "3.1.1",
+  "version": "4.0.0",
 
   "description": "Firefox Multi-Account Containers helps you keep all the parts of your online life contained in different tabs. Custom labels and color-coded tabs help keep different activities — like online shopping, travel planning, or checking work email — separate.",
   "icons": {