--- a/browser/app/profile/firefox.js
+++ b/browser/app/profile/firefox.js
@@ -1634,16 +1634,17 @@ pref("browser.crashReports.unsubmittedCh
 
 // Preferences for the form autofill system extension
 #ifdef NIGHTLY_BUILD
 pref("extensions.formautofill.experimental", true);
 #else
 pref("extensions.formautofill.experimental", false);
 #endif
 pref("extensions.formautofill.addresses.enabled", true);
+pref("extensions.formautofill.heuristics.enabled", false);
 pref("extensions.formautofill.loglevel", "Warn");
 
 // Whether or not to restore a session with lazy-browser tabs.
 pref("browser.sessionstore.restore_tabs_lazily", true);
 
 // Enable safebrowsing v4 tables (suffixed by "-proto") update.
 #ifdef NIGHTLY_BUILD
 pref("urlclassifier.malwareTable", "goog-malware-shavar,goog-unwanted-shavar,goog-malware-proto,goog-unwanted-proto,test-malware-simple,test-unwanted-simple");

--- a/browser/extensions/formautofill/FormAutofillHeuristics.jsm
+++ b/browser/extensions/formautofill/FormAutofillHeuristics.jsm
@@ -7,22 +7,25 @@
  */
 
 "use strict";
 
 this.EXPORTED_SYMBOLS = ["FormAutofillHeuristics"];
 
 const {classes: Cc, interfaces: Ci, utils: Cu, results: Cr} = Components;
 
+Cu.import("resource://gre/modules/Services.jsm");
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://formautofill/FormAutofillUtils.jsm");
 
 this.log = null;
 FormAutofillUtils.defineLazyLogGetter(this, this.EXPORTED_SYMBOLS[0]);
 
+const PREF_HEURISTICS_ENABLED = "extensions.formautofill.heuristics.enabled";
+
 /**
  * Returns the autocomplete information of fields according to heuristics.
  */
 this.FormAutofillHeuristics = {
   FIELD_GROUPS: {
     NAME: [
       "name",
       "given-name",
@@ -142,16 +145,20 @@ this.FormAutofillHeuristics = {
 
     let info = element.getAutocompleteInfo();
     // An input[autocomplete="on"] will not be early return here since it stll
     // needs to find the field name.
     if (info && info.fieldName && info.fieldName != "on") {
       return info;
     }
 
+    if (!this._prefEnabled) {
+      return null;
+    }
+
     // "email" type of input is accurate for heuristics to determine its Email
     // field or not. However, "tel" type is used for ZIP code for some web site
     // (e.g. HomeDepot, BestBuy), so "tel" type should be not used for "tel"
     // prediction.
     if (element.type == "email") {
       return {
         fieldName: "email",
         section: "",
@@ -193,8 +200,16 @@ XPCOMUtils.defineLazyGetter(this.FormAut
   let sandbox = {};
   let scriptLoader = Cc["@mozilla.org/moz/jssubscript-loader;1"]
                        .getService(Ci.mozIJSSubScriptLoader);
   const HEURISTICS_REGEXP = "chrome://formautofill/content/heuristicsRegexp.js";
   scriptLoader.loadSubScript(HEURISTICS_REGEXP, sandbox, "utf-8");
   return sandbox.HeuristicsRegExp.RULES;
 });
 
+XPCOMUtils.defineLazyGetter(this.FormAutofillHeuristics, "_prefEnabled", () => {
+  return Services.prefs.getBoolPref(PREF_HEURISTICS_ENABLED);
+});
+
+Services.prefs.addObserver(PREF_HEURISTICS_ENABLED, () => {
+  this.FormAutofillHeuristics._prefEnabled = Services.prefs.getBoolPref(PREF_HEURISTICS_ENABLED);
+});
+

--- a/browser/extensions/formautofill/test/unit/head.js
+++ b/browser/extensions/formautofill/test/unit/head.js
@@ -115,14 +115,16 @@ function runHeuristicsTest(patterns, fix
         });
       });
     });
   });
 }
 
 add_task(function* head_initialize() {
   Services.prefs.setBoolPref("extensions.formautofill.experimental", true);
+  Services.prefs.setBoolPref("extensions.formautofill.heuristics.enabled", true);
 
   // Clean up after every test.
   do_register_cleanup(function head_cleanup() {
     Services.prefs.clearUserPref("extensions.formautofill.experimental");
+    Services.prefs.clearUserPref("extensions.formautofill.heuristics.enabled");
   });
 });