diff --git a/src/blocker.js b/src/blocker.js
index 76b3500..678e3b3 100644
--- a/src/blocker.js
+++ b/src/blocker.js
@@ -1,9 +1,13 @@
-var currentPatterns = [];
-
 function blockRequest(details) {
-  console.log("Blocked: ", details.url);
+  if (probability > Math.random()) {
+    console.log("Blocked: ", details.url);
+    return {
+      cancel: true
+    };  
+  }
+  console.log("Not blocked: ", details.url);
   return {
-    cancel: true
+    cancel: false
   };
 }
 
@@ -12,12 +16,12 @@ function isValidPattern(urlPattern) {
   return !!urlPattern.match(validPattern);
 }
 
-function updateFilters() {
+function updateFilters(urls) {
   if (chrome.webRequest.onBeforeRequest.hasListener(blockRequest)) {
     chrome.webRequest.onBeforeRequest.removeListener(blockRequest);
   }
 
-  var validPatterns = currentPatterns.filter(isValidPattern);
+  var validPatterns = patterns.filter(isValidPattern);
 
   if (validPatterns.length) {
     try{
@@ -31,23 +35,27 @@ function updateFilters() {
 }
 
 function load(callback) {
-  chrome.storage.sync.get('blocked_patterns', function(data) {
-    callback(data['blocked_patterns'] || []);
+  chrome.storage.sync.get(['blocked_patterns', 'probability'], function(data) {
+    callback(data['blocked_patterns'] || [], data['probability'] || 1);
   });
 }
 
-function save(newPatterns, callback) {
-  currentPatterns = newPatterns;
+function save(newPatterns, newProbability, callback) {
+  patterns = newPatterns;
+  probability = newProbability;
+
   chrome.storage.sync.set({
-    'blocked_patterns': newPatterns
+    'blocked_patterns': newPatterns,
+    'probability': probability
   }, function() {
     updateFilters();
     callback.call();
   });
 }
 
-load(function(patterns) {
-  currentPatterns = patterns;
+load(function(pat, prob) {
+  patterns = pat;
+  probability = prob;
   updateFilters();
 });
 
diff --git a/src/popup.html b/src/popup.html
index ead0b84..f94ec3e 100644
--- a/src/popup.html
+++ b/src/popup.html
@@ -35,6 +35,14 @@ <h3>{{patterns.length}} Pattern(s) (<a href="javascript:void(0)" ng-click="add()
       <p class="bg-warning text-warning">Url patterns must comply with the format specified at <a href="https://developer.chrome.com/extensions/match_patterns">https://developer.chrome.com/extensions/match_patterns</a> (ex: <strong>*://evilsite.com/*</strong>).
       Invalid patterns will be ignored.</p>
 
+      <hr />
+
+      <div class="form-group">
+        <label for="probability">Probability</label>
+        <input type="number" min="0.0" max="1.0" step="0.1" class="form-control" ng-model="probability" />
+      </div>
+
+
       <hr />
 
       <div>
diff --git a/src/popup.js b/src/popup.js
index 4c4a63c..350bee2 100644
--- a/src/popup.js
+++ b/src/popup.js
@@ -17,6 +17,7 @@ app.controller('PopupController', function($scope) {
             }
         };
     });
+    $scope.probability = $scope.backgroundPage.probability;
 
     $scope.remove = function(patternToRemove) {
         var index = $scope.patterns.indexOf(patternToRemove);
@@ -37,9 +38,11 @@ app.controller('PopupController', function($scope) {
             return x.pattern;
         });
 
-        $scope.backgroundPage.save(patterns, function() {
+        var probability = $scope.probability;
+
+        $scope.backgroundPage.save(patterns, probability, function() {
             $scope.$apply(function() {
-                $scope.success('Patterns saved successfully!');
+                $scope.success('Patterns saved successfully!!');
             });
         });
     };