Index: gc_lang/fr/build.py
==================================================================
--- gc_lang/fr/build.py
+++ gc_lang/fr/build.py
@@ -91,10 +91,12 @@
             hZip.write(spDict+"/"+sp+"/"+sp+".dic", "content/dictionaries/"+sp+"/"+sp+".dic")
             hZip.write(spDict+"/"+sp+"/"+sp+".aff", "content/dictionaries/"+sp+"/"+sp+".aff")
     hZip.close()
     spfDebugProfile = dVars['win_tb_debug_extension_path']  if platform.system() == "Windows"  else dVars['linux_tb_debug_extension_path']
     helpers.unzip(spfZip, spfDebugProfile)
+    spfBetaProfile = dVars['win_tb_beta_extension_path']  if platform.system() == "Windows"  else dVars['linux_tb_beta_extension_path']
+    helpers.unzip(spfZip, spfBetaProfile)
 
 
 def _createOptionsForThunderbird (dVars):
     dVars['sXULTabs'] = ""
     dVars['sXULTabPanels'] = ""

Index: gc_lang/fr/config.ini
==================================================================
--- gc_lang/fr/config.ini
+++ gc_lang/fr/config.ini
@@ -46,12 +46,18 @@
 linux_fx_nightly_path = /usr/bin/firefox
 
 # Thunderbird
 tb_identifier = French-GC-TB@grammalecte.net
 tb_name = Grammalecte [fr]
+win_tb_path = C:\Program Files (x86)\Mozilla Thunderbird\thunderbird.exe
+win_tb_beta_path = C:\Program Files (x86)\Mozilla Thunderbird (Beta)\thunderbird.exe
+linux_tb_path = /usr/bin/thunderbird
+linux_tb_beta_path = /usr/bin/thunderbird
 win_tb_debug_extension_path = D:\_temp\tb-debug.profile\extensions\French-GC-TB@grammalecte.net
 linux_tb_debug_extension_path = ~/tb-debug.profile/extensions/French-GC-TB@grammalecte.net
+win_tb_beta_extension_path = D:\_temp\tb-beta.profile\extensions\French-GC-TB@grammalecte.net
+linux_tb_beta_extension_path = ~/tb-beta.profile/extensions/French-GC-TB@grammalecte.net
 # Set Thunderbird folder in your PATH variable
 # Create a local profile:
 #     	thunderbird -CreateProfile "debug _build\tb-debug.profile"
 # Or you can use the GUI with:
 #	 	thunderbird -P

Index: gc_lang/fr/tb/chrome.manifest
==================================================================
--- gc_lang/fr/tb/chrome.manifest
+++ gc_lang/fr/tb/chrome.manifest
@@ -4,6 +4,6 @@
 resource grammalecte ./grammalecte-js/
 locale	grammarchecker	fr	locale/fr/
 locale	grammarchecker	en	locale/en/
 skin	grammarchecker	classic/1.0	skin/
 overlay	chrome://messenger/content/messengercompose/messengercompose.xul	chrome://grammarchecker/content/overlay.xul
-style	chrome://global/content/customizeToolbar.xul	chrome://grammarchecker/content/overlay.css
+style	chrome://messenger/content/customizeToolbar.xul	chrome://grammarchecker/content/overlay.css

Index: gc_lang/fr/tb/content/about.xul
==================================================================
--- gc_lang/fr/tb/content/about.xul
+++ gc_lang/fr/tb/content/about.xul
@@ -32,7 +32,7 @@
   <image src="chrome://grammarchecker/skin/Algoo_logo.png" style="cursor: pointer;"
     onclick="openInTabURL('https://www.algoo.fr/?from=grammalecte-tb');" />
   <label id="contrib" value="&contrib;"
     onclick="openInTabURL('https://www.dicollecte.org/#thanks');" />
 
-  <script type="application/x-javascript" src="about.js"/>
+  <script type="application/javascript" src="about.js"/>
 </dialog>

Index: gc_lang/fr/tb/content/conjugueur.xul
==================================================================
--- gc_lang/fr/tb/content/conjugueur.xul
+++ gc_lang/fr/tb/content/conjugueur.xul
@@ -152,7 +152,7 @@
         <label id="condb6" class="cj">.</label>
       </groupbox>
     </column>
   </columns>
 
-  <script type="application/x-javascript" src="conjugueur.js"/>
+  <script type="application/javascript" src="conjugueur.js"/>
 </dialog>

Index: gc_lang/fr/tb/content/gc_options.xul
==================================================================
--- gc_lang/fr/tb/content/gc_options.xul
+++ gc_lang/fr/tb/content/gc_options.xul
@@ -29,8 +29,8 @@
     <tabpanels>
 ${sXULTabPanels}
     </tabpanels>
   </tabbox>
 
-  <script type="application/x-javascript" src="gc_options.js" />
+  <script type="application/javascript" src="gc_options.js" />
 
 </dialog>

Index: gc_lang/fr/tb/content/overlay.xul
==================================================================
--- gc_lang/fr/tb/content/overlay.xul
+++ gc_lang/fr/tb/content/overlay.xul
@@ -4,14 +4,14 @@
 <!DOCTYPE overlay SYSTEM "chrome://grammarchecker/locale/overlay.dtd">
 
 <overlay id="grammarchecker-overlay"
          xmlns="http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul">
 
-  <script type="application/x-javascript" src="chrome://global/content/globalOverlay.js"/>
-  <script type="application/x-javascript" src="overlay.js"/>
-  <script type="application/x-javascript" src="spellchecker.js"/>
-  <script type="application/x-javascript" src="editor.js"/>
+  <script type="application/javascript" src="chrome://global/content/globalOverlay.js"/>
+  <script type="application/javascript" src="overlay.js"/>
+  <script type="application/javascript" src="spellchecker.js"/>
+  <script type="application/javascript" src="editor.js"/>
 
   <stringbundleset id="stringbundleset">
     <stringbundle id="grammarchecker-strings" src="chrome://grammarchecker/locale/grammarchecker.properties"/>
   </stringbundleset>
 

Index: gc_lang/fr/tb/content/spell_options.xul
==================================================================
--- gc_lang/fr/tb/content/spell_options.xul
+++ gc_lang/fr/tb/content/spell_options.xul
@@ -32,9 +32,9 @@
     <description class="dicdescr">&option.reform.descr;</description>
     <checkbox id="fr-FR-classic-reform" class="option" label="&option.allvar.label;" />
     <description class="dicdescr">&option.allvar.descr;</description>
   </groupbox>
 
-  <script type="application/x-javascript" src="spell_options.js"/>
-  <script type="application/x-javascript" src="spellchecker.js"/>
+  <script type="application/javascript" src="spell_options.js"/>
+  <script type="application/javascript" src="spellchecker.js"/>
 
 </dialog>

Index: graphspell-js/helpers.js
==================================================================
--- graphspell-js/helpers.js
+++ graphspell-js/helpers.js
@@ -51,18 +51,11 @@
         // load ressources in workers (suggested by Mozilla extensions reviewers)
         // for more options have a look here: https://gist.github.com/Noitidart/ec1e6b9a593ec7e3efed
         // if not in workers, use sdk/data.load() instead
         try {
             let xRequest;
-            if (typeof XMLHttpRequest !== "undefined") {
-                xRequest = new XMLHttpRequest();
-            } else {
-                // JS sucks again… necessary for Thunderbird
-                let { Cc, Ci } = require("chrome");
-                xRequest = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance();
-                xRequest.QueryInterface(Ci.nsIXMLHttpRequest);
-            }
+            xRequest = new XMLHttpRequest();
             xRequest.open('GET', spf, false); // 3rd arg is false for synchronous, sync is acceptable in workers
             xRequest.overrideMimeType('text/json');
             xRequest.send();
             return xRequest.responseText;
         }

Index: make.py
==================================================================
--- make.py
+++ make.py
@@ -363,10 +363,11 @@
     xParser.add_argument("-aed", "--add_extended_dictionary", help="add extended dictionary to the build", action="store_true")
     xParser.add_argument("-apd", "--add_personal_dictionary", help="add personal dictionary to the build", action="store_true")
     xParser.add_argument("-fx", "--firefox", help="Launch Firefox Developper for WebExtension testing", action="store_true")
     xParser.add_argument("-we", "--web_ext", help="Launch Firefox Nightly for WebExtension testing", action="store_true")
     xParser.add_argument("-tb", "--thunderbird", help="Launch Thunderbird", action="store_true")
+    xParser.add_argument("-tbb", "--thunderbird_beta", help="Launch Thunderbird Beta", action="store_true")
     xParser.add_argument("-i", "--install", help="install the extension in Writer (path of unopkg must be set in config.ini)", action="store_true")
     xArgs = xParser.parse_args()
 
     if xArgs.build_data:
         xArgs.build_data_before = True
@@ -448,15 +449,21 @@
                         spfFirefox = dVars['win_fx_nightly_path']  if platform.system() == "Windows"  else dVars['linux_fx_nightly_path']
                     os.system(r'web-ext run --firefox="' + spfFirefox + '" --browser-console --firefox-profile=debug')            
 
             # Thunderbird
             if xArgs.thunderbird:
-                os.system("thunderbird -jsconsole -P debug")
+                spfThunderbird = '"'+dVars['win_tb_path']+'"'  if platform.system() == "Windows"  else dVars['linux_tb_path']
+                print(spfThunderbird)
+                os.system(spfThunderbird + ' -jsconsole -P debug')
+            if xArgs.thunderbird_beta:
+                spfThunderbird = '"'+dVars['win_tb_beta_path']+'"'  if platform.system() == "Windows"  else dVars['linux_tb_beta_path']
+                print(spfThunderbird)
+                os.system(spfThunderbird + ' -jsconsole -P beta')
         else:
             print("Folder not found: gc_lang/"+sLang)
 
     oNow = datetime.datetime.now()
     print("============== MAKE GRAMMALECTE [finished] at {0.hour:>2} h {0.minute:>2} min {0.second:>2} s ==============".format(oNow))
 
 
 if __name__ == '__main__':
     main()