diff --git a/.gitignore b/.gitignore
index 1ee23e6e..73d5449e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1 @@
-/install.rdf
 /exchangecalendar-v*.xpi
diff --git a/Makefile b/Makefile
index c16c0a2c..d978b9bd 100644
--- a/Makefile
+++ b/Makefile
@@ -1,5 +1,5 @@
-version = $(shell cat VERSION)
-excludefromxpi = .git/\* .gitignore \*/.gitignore .tx/\* \*.xpi \*.sh update\*.txt Makefile VERSION install.rdf.template
+version = $(shell jq -r '.version' manifest.json)
+excludefromxpi = .git/\* .gitignore \*/.gitignore .tx/\* \*.xpi \*.sh update\*.txt Makefile
 releasebranch = ec-4.0
 update = disable
 xpi = exchangecalendar-v$(version).xpi
@@ -9,13 +9,10 @@ xpi = exchangecalendar-v$(version).xpi
 # Default target is build package
 build: $(xpi)
 
-$(xpi): install.rdf defaults/preferences/update.js
+$(xpi): defaults/preferences/update.js
 	rm -f $@
 	zip -r $@ -x $(excludefromxpi) -- .
 
-install.rdf: install.rdf.template
-	sed 's/@VERSION@/$(version)/g' $< > $@
-
 defaults/preferences/update.js:
 	cp defaults/preferences/update_$(update).txt $@
 
diff --git a/VERSION b/VERSION
deleted file mode 100644
index 922d4daa..00000000
--- a/VERSION
+++ /dev/null
@@ -1 +0,0 @@
-4.0.0-beta5
diff --git a/install.rdf.template b/install.rdf.template
deleted file mode 100644
index 78ebc2fb..00000000
--- a/install.rdf.template
+++ /dev/null
@@ -1,53 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<RDF xmlns="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
-     xmlns:em="http://www.mozilla.org/2004/em-rdf#">
-    <Description about="urn:mozilla:install-manifest">
-        <em:id>exchangecalendar@extensions.1st-setup.nl</em:id>
-        <em:version>@VERSION@</em:version>
-        <em:targetApplication>
-            <Description>
-                <!-- Thunderbird -->
-                <em:id>{3550f703-e582-4d05-9a08-453d09bdfdc6}</em:id>
-                <em:minVersion>52.0.0</em:minVersion>
-                <em:maxVersion>52.*.*</em:maxVersion>
-            </Description>
-        </em:targetApplication>
-        <em:targetApplication>
-            <Description>
-                <!-- Seamonkey -->
-                <em:id>{92650c4d-4b8e-4d2a-b7eb-24ecf4f6b63a}</em:id>
-                <em:minVersion>2.49.*</em:minVersion>
-                <em:maxVersion>2.49.*</em:maxVersion>
-            </Description>
-        </em:targetApplication>
-        <em:unpack>true</em:unpack>
-        <em:name>Exchange Calendar</em:name>
-        <em:homepageURL>https://github.com/ExchangeCalendar/exchangecalendar</em:homepageURL>
-        <em:iconURL>chrome://exchangecommon-common/skin/images/lightningexchangecalendar.png</em:iconURL>
-        <em:creator>Michel Verbraak</em:creator>
-        <em:developer>ExchangeCalendar community</em:developer>
-        <em:translator>Michel Verbraak (nl)</em:translator>
-        <em:translator>Michel Verbraak (en-US)</em:translator>
-        <em:translator>Dominique Fillon (fr-FR)</em:translator>
-        <em:translator>Christian A. Meyer (de)</em:translator>
-        <em:translator>Björn Töpper (de)</em:translator>
-        <em:translator>Hiroshi Miura (ja-JP)</em:translator>
-        <em:translator>Alexey Sinitsyn (ru)</em:translator>
-        <em:translator>Alessandro Menti (it-IT)</em:translator>
-        <em:translator>Engin Özkan (tr)</em:translator>
-        <em:localized>
-            <Description>
-                <em:locale>en</em:locale>
-                <em:name>Exchange Calendar</em:name>
-                <em:description>Allows you to sync calendars, tasks, and contacts with Microsoft Exchange.</em:description>
-            </Description>
-        </em:localized>
-        <em:localized>
-            <Description>
-                <em:locale>fr</em:locale>
-                <em:name>Exchange Calendar</em:name>
-                <em:description>Vous permet de synchroniser les calendriers, tâches et contactes avec Microsoft Exchange.</em:description>
-            </Description>
-        </em:localized>
-    </Description>
-</RDF>
diff --git a/manifest.json b/manifest.json
new file mode 100644
index 00000000..d6146090
--- /dev/null
+++ b/manifest.json
@@ -0,0 +1,18 @@
+{
+  "manifest_version": 2,
+  "applications": {
+    "gecko": {
+      "id": "github.com_exchangecalendar@community.invalid",
+      "strict_min_version": "68.0"
+    }
+  },
+  "name": "Exchange Calendar",
+  "description": "Synchronize calendars, tasks, and contacts with Microsoft Exchange.",
+  "version": "4.0.0.5",
+  "version_name": "4.0.0-beta5",
+  "icons": {
+    "32": "common/theme/common/images/lightningexchangecalendar.png"
+  },
+  "homepage_url": "https://github.com/ExchangeCalendar/exchangecalendar",
+  "author": "ExchangeCalendar community"
+}