diff --git a/modules/appnexusBidAdapter.js b/modules/appnexusBidAdapter.js
index 67388848815..d0f4774185e 100644
--- a/modules/appnexusBidAdapter.js
+++ b/modules/appnexusBidAdapter.js
@@ -33,6 +33,9 @@ const NATIVE_MAPPING = {
 const SOURCE = 'pbjs';
 const MAX_IMPS_PER_REQUEST = 15;
 const mappingFileUrl = '//acdn.adnxs.com/prebid/appnexus-mapping/mappings.json';
+const SCRIPT_TAG_START = '<script';
+const VIEWABILITY_URL_START = /http:\/\/cdn\.adnxs\.com\/v/;
+const VIEWABILITY_FILE_NAME = 'trk.js';
 
 export const spec = {
   code: BIDDER_CODE,
@@ -283,6 +286,16 @@ export const spec = {
     }
 
     return params;
+  },
+
+  /**
+   * Add element selector to javascript tracker to improve native viewability
+   * @param {Bid} bid
+   */
+  onBidWon: function(bid) {
+    if (bid.native) {
+      reloadViewabilityScriptWithCorrectParameters(bid);
+    }
   }
 }
 
@@ -296,6 +309,91 @@ function deleteValues(keyPairObj) {
   }
 }
 
+function reloadViewabilityScriptWithCorrectParameters(bid) {
+  let viewJsPayload = getAppnexusViewabilityScriptFromJsTrackers(bid.native.javascriptTrackers);
+
+  if (viewJsPayload) {
+    let prebidParams = 'pbjs_adid=' + bid.adId + ';pbjs_auc=' + bid.adUnitCode;
+
+    let jsTrackerSrc = getViewabilityScriptUrlFromPayload(viewJsPayload)
+
+    let newJsTrackerSrc = jsTrackerSrc.replace('dom_id=%native_dom_id%', prebidParams);
+
+    // find iframe containing script tag
+    let frameArray = document.getElementsByTagName('iframe');
+
+    // boolean var to modify only one script. That way if there are muliple scripts,
+    // they won't all point to the same creative.
+    let modifiedAScript = false;
+
+    // first, loop on all ifames
+    for (let i = 0; i < frameArray.length && !modifiedAScript; i++) {
+      let currentFrame = frameArray[i];
+      try {
+        // IE-compatible, see https://stackoverflow.com/a/3999191/2112089
+        let nestedDoc = currentFrame.contentDocument || currentFrame.contentWindow.document;
+
+        if (nestedDoc) {
+          // if the doc is present, we look for our jstracker
+          let scriptArray = nestedDoc.getElementsByTagName('script');
+          for (let j = 0; j < scriptArray.length && !modifiedAScript; j++) {
+            let currentScript = scriptArray[j];
+            if (currentScript.getAttribute('data-src') == jsTrackerSrc) {
+              currentScript.setAttribute('src', newJsTrackerSrc);
+              currentScript.setAttribute('data-src', '');
+              if (currentScript.removeAttribute) {
+                currentScript.removeAttribute('data-src');
+              }
+              modifiedAScript = true;
+            }
+          }
+        }
+      } catch (exception) {
+        // trying to access a cross-domain iframe raises a SecurityError
+        // this is expected and ignored
+        if (!(exception instanceof DOMException && exception.name === 'SecurityError')) {
+          // all other cases are raised again to be treated by the calling function
+          throw exception;
+        }
+      }
+    }
+  }
+}
+
+function strIsAppnexusViewabilityScript(str) {
+  let regexMatchUrlStart = str.match(VIEWABILITY_URL_START);
+  let viewUrlStartInStr = regexMatchUrlStart != null && regexMatchUrlStart.length >= 1;
+
+  let regexMatchFileName = str.match(VIEWABILITY_FILE_NAME);
+  let fileNameInStr = regexMatchFileName != null && regexMatchFileName.length >= 1;
+
+  return str.startsWith(SCRIPT_TAG_START) && fileNameInStr && viewUrlStartInStr;
+}
+
+function getAppnexusViewabilityScriptFromJsTrackers(jsTrackerArray) {
+  let viewJsPayload;
+  if (utils.isStr(jsTrackerArray) && strIsAppnexusViewabilityScript(jsTrackerArray)) {
+    viewJsPayload = jsTrackerArray;
+  } else if (utils.isArray(jsTrackerArray)) {
+    for (let i = 0; i < jsTrackerArray.length; i++) {
+      let currentJsTracker = jsTrackerArray[i];
+      if (strIsAppnexusViewabilityScript(currentJsTracker)) {
+        viewJsPayload = currentJsTracker;
+      }
+    }
+  }
+  return viewJsPayload;
+}
+
+function getViewabilityScriptUrlFromPayload(viewJsPayload) {
+  // extracting the content of the src attribute
+  // -> substring between src=" and "
+  let indexOfFirstQuote = viewJsPayload.indexOf('src="') + 5; // offset of 5: the length of 'src=' + 1
+  let indexOfSecondQuote = viewJsPayload.indexOf('"', indexOfFirstQuote);
+  let jsTrackerSrc = viewJsPayload.substring(indexOfFirstQuote, indexOfSecondQuote);
+  return jsTrackerSrc;
+}
+
 function formatRequest(payload, bidderRequest) {
   let request = [];
 
@@ -415,6 +513,22 @@ function newBid(serverBid, rtbBid, bidderRequest) {
     }
   } else if (rtbBid.rtb[NATIVE]) {
     const nativeAd = rtbBid.rtb[NATIVE];
+
+    // setting up the jsTracker:
+    // we put it as a data-src attribute so that the tracker isn't called
+    // until we have the adId (see onBidWon)
+    let jsTrackerDisarmed = rtbBid.viewability.config.replace('src=', 'data-src=');
+
+    let jsTrackers = nativeAd.javascript_trackers;
+
+    if (jsTrackers == undefined) {
+      jsTrackers = jsTrackerDisarmed;
+    } else if (utils.isStr(jsTrackers)) {
+      jsTrackers = [jsTrackers, jsTrackerDisarmed];
+    } else {
+      jsTrackers.push(jsTrackerDisarmed);
+    }
+
     bid[NATIVE] = {
       title: nativeAd.title,
       body: nativeAd.desc,
@@ -433,7 +547,7 @@ function newBid(serverBid, rtbBid, bidderRequest) {
       displayUrl: nativeAd.displayurl,
       clickTrackers: nativeAd.link.click_trackers,
       impressionTrackers: nativeAd.impression_trackers,
-      javascriptTrackers: nativeAd.javascript_trackers
+      javascriptTrackers: jsTrackers
     };
     if (nativeAd.main_img) {
       bid['native'].image = {
diff --git a/src/native.js b/src/native.js
index c9a67ca7541..6252eb133b3 100644
--- a/src/native.js
+++ b/src/native.js
@@ -132,7 +132,6 @@ export function nativeBidIsValid(bid, bidRequests) {
  */
 export function fireNativeTrackers(message, adObject) {
   let trackers;
-
   if (message.action === 'click') {
     trackers = adObject['native'] && adObject['native'].clickTrackers;
   } else {
diff --git a/test/spec/modules/appnexusBidAdapter_spec.js b/test/spec/modules/appnexusBidAdapter_spec.js
index 30d2dc08159..e1cca8c05ff 100644
--- a/test/spec/modules/appnexusBidAdapter_spec.js
+++ b/test/spec/modules/appnexusBidAdapter_spec.js
@@ -665,6 +665,9 @@ describe('AppNexusAdapter', function () {
               'cpm_publisher_currency': 0.5,
               'publisher_currency_code': '$',
               'client_initiated_ad_counting': true,
+              'viewability': {
+                'config': '<script type=\'text/javascript\' async=\'true\' src=\'http://cdn.adnxs.com/v/s/152/trk.js#v;vk=appnexus.com-omid;tv=native1-18h;dom_id=%native_dom_id%;st=0;d=1x1;vc=iab;vid_ccr=1;tag_id=13232354;cb=http%3A%2F%2Fams1-ib.adnxs.com%2Fvevent%3Freferrer%3Dhttp%253A%252F%252Ftestpages-pmahe.tp.adnxs.net%252F01_basic_single%26e%3DwqT_3QLNB6DNAwAAAwDWAAUBCLfl_-MFEMStk8u3lPTjRxih88aF0fq_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-CoAcgDANgD8ao-4AMA6AMA-AMBgAQAkgQNL3V0L3YzL3ByZWJpZJgEAKIECjEwLjIuMTIuMzioBIqpB7IEDggAEAEYACAAKAAwADgCuAQAwAQAyAQA0gQOOTMyNSNBTVMxOjQzMjDaBAIIAeAEAfAEg8u-LogFAZgFAKAF______8BAxgBwAUAyQUABQEU8D_SBQkJBQt8AAAA2AUB4AUB8AWZ9CH6BQQIABAAkAYBmAYAuAYAwQYBITAAAPA_yAYA2gYWChAAOgEAGBAAGADgBgw.%26s%3D971dce9d49b6bee447c8a58774fb30b40fe98171;ts=1551889079;cet=0;cecb=\'></script>'
+              },
               'rtb': {
                 'banner': {
                   'content': '<!-- Creative -->',
@@ -744,7 +747,8 @@ describe('AppNexusAdapter', function () {
               'video': {
                 'content': '<!-- Creative -->'
               }
-            }
+            },
+            'javascriptTrackers': '<script type=\'text/javascript\' async=\'true\' src=\'http://cdn.adnxs.com/v/s/152/trk.js#v;vk=appnexus.com-omid;tv=native1-18h;dom_id=%native_dom_id%;st=0;d=1x1;vc=iab;vid_ccr=1;tag_id=13232354;cb=http%3A%2F%2Fams1-ib.adnxs.com%2Fvevent%3Freferrer%3Dhttp%253A%252F%252Ftestpages-pmahe.tp.adnxs.net%252F01_basic_single%26e%3DwqT_3QLNB6DNAwAAAwDWAAUBCLfl_-MFEMStk8u3lPTjRxih88aF0fq_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-CoAcgDANgD8ao-4AMA6AMA-AMBgAQAkgQNL3V0L3YzL3ByZWJpZJgEAKIECjEwLjIuMTIuMzioBIqpB7IEDggAEAEYACAAKAAwADgCuAQAwAQAyAQA0gQOOTMyNSNBTVMxOjQzMjDaBAIIAeAEAfAEg8u-LogFAZgFAKAF______8BAxgBwAUAyQUABQEU8D_SBQkJBQt8AAAA2AUB4AUB8AWZ9CH6BQQIABAAkAYBmAYAuAYAwQYBITAAAPA_yAYA2gYWChAAOgEAGBAAGADgBgw.%26s%3D971dce9d49b6bee447c8a58774fb30b40fe98171;ts=1551889079;cet=0;cecb=\'></script>'
           }]
         }]
       };
@@ -775,6 +779,9 @@ describe('AppNexusAdapter', function () {
                 'content': '<!-- Creative -->',
                 'duration_ms': 30000,
               }
+            },
+            'viewability': {
+              'config': '<script type=\'text/javascript\' async=\'true\' src=\'http://cdn.adnxs.com/v/s/152/trk.js#v;vk=appnexus.com-omid;tv=native1-18h;dom_id=%native_dom_id%;st=0;d=1x1;vc=iab;vid_ccr=1;tag_id=13232354;cb=http%3A%2F%2Fams1-ib.adnxs.com%2Fvevent%3Freferrer%3Dhttp%253A%252F%252Ftestpages-pmahe.tp.adnxs.net%252F01_basic_single%26e%3DwqT_3QLNB6DNAwAAAwDWAAUBCLfl_-MFEMStk8u3lPTjRxih88aF0fq_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-CoAcgDANgD8ao-4AMA6AMA-AMBgAQAkgQNL3V0L3YzL3ByZWJpZJgEAKIECjEwLjIuMTIuMzioBIqpB7IEDggAEAEYACAAKAAwADgCuAQAwAQAyAQA0gQOOTMyNSNBTVMxOjQzMjDaBAIIAeAEAfAEg8u-LogFAZgFAKAF______8BAxgBwAUAyQUABQEU8D_SBQkJBQt8AAAA2AUB4AUB8AWZ9CH6BQQIABAAkAYBmAYAuAYAwQYBITAAAPA_yAYA2gYWChAAOgEAGBAAGADgBgw.%26s%3D971dce9d49b6bee447c8a58774fb30b40fe98171;ts=1551889079;cet=0;cecb=\'></script>'
             }
           }]
         }]
@@ -831,7 +838,8 @@ describe('AppNexusAdapter', function () {
         'saleprice': 'FREE',
         'phone': '1234567890',
         'address': '28 W 23rd St, New York, NY 10010',
-        'privacy_link': 'http://appnexus.com/?url=privacy_url'
+        'privacy_link': 'http://appnexus.com/?url=privacy_url',
+        'javascriptTrackers': '<script type=\'text/javascript\' async=\'true\' src=\'http://cdn.adnxs.com/v/s/152/trk.js#v;vk=appnexus.com-omid;tv=native1-18h;dom_id=;css_selector=.pb-click;st=0;d=1x1;vc=iab;vid_ccr=1;tag_id=13232354;cb=http%3A%2F%2Fams1-ib.adnxs.com%2Fvevent%3Freferrer%3Dhttp%253A%252F%252Ftestpages-pmahe.tp.adnxs.net%252F01_basic_single%26e%3DwqT_3QLNB6DNAwAAAwDWAAUBCLfl_-MFEMStk8u3lPTjRxih88aF0fq_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-CoAcgDANgD8ao-4AMA6AMA-AMBgAQAkgQNL3V0L3YzL3ByZWJpZJgEAKIECjEwLjIuMTIuMzioBIqpB7IEDggAEAEYACAAKAAwADgCuAQAwAQAyAQA0gQOOTMyNSNBTVMxOjQzMjDaBAIIAeAEAfAEg8u-LogFAZgFAKAF______8BAxgBwAUAyQUABQEU8D_SBQkJBQt8AAAA2AUB4AUB8AWZ9CH6BQQIABAAkAYBmAYAuAYAwQYBITAAAPA_yAYA2gYWChAAOgEAGBAAGADgBgw.%26s%3D971dce9d49b6bee447c8a58774fb30b40fe98171;ts=1551889079;cet=0;cecb=\'></script>'
       };
       let bidderRequest = {
         bids: [{
diff --git a/test/spec/unit/pbjs_api_spec.js b/test/spec/unit/pbjs_api_spec.js
index d4daec0c266..c73604cac82 100644
--- a/test/spec/unit/pbjs_api_spec.js
+++ b/test/spec/unit/pbjs_api_spec.js
@@ -434,7 +434,9 @@ describe('Unit: Prebid Module', function () {
             'trackers': [{
               'impression_urls': ['http://lax1-ib.adnxs.com/impression']
             }]
-          }
+          },
+          'viewability': {
+            'config': '<script type=\'text/javascript\' async=\'true\' src=\'http://cdn.adnxs.com/v/s/152/trk.js#v;vk=appnexus.com-omid;tv=native1-18h;dom_id=%native_dom_id%;st=0;d=1x1;vc=iab;vid_ccr=1;tag_id=13232354;cb=http%3A%2F%2Fams1-ib.adnxs.com%2Fvevent%3Freferrer%3Dhttp%253A%252F%252Ftestpages-pmahe.tp.adnxs.net%252F01_basic_single%26e%3DwqT_3QLNB6DNAwAAAwDWAAUBCLfl_-MFEMStk8u3lPTjRxih88aF0fq_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-CoAcgDANgD8ao-4AMA6AMA-AMBgAQAkgQNL3V0L3YzL3ByZWJpZJgEAKIECjEwLjIuMTIuMzioBIqpB7IEDggAEAEYACAAKAAwADgCuAQAwAQAyAQA0gQOOTMyNSNBTVMxOjQzMjDaBAIIAeAEAfAEg8u-LogFAZgFAKAF______8BAxgBwAUAyQUABQEU8D_SBQkJBQt8AAAA2AUB4AUB8AWZ9CH6BQQIABAAkAYBmAYAuAYAwQYBITAAAPA_yAYA2gYWChAAOgEAGBAAGADgBgw.%26s%3D971dce9d49b6bee447c8a58774fb30b40fe98171;ts=1551889079;cet=0;cecb=\'></script>'}
         }]
       }]
     };
@@ -574,7 +576,9 @@ describe('Unit: Prebid Module', function () {
             'trackers': [{
               'impression_urls': ['http://lax1-ib.adnxs.com/impression']
             }]
-          }
+          },
+          'viewability': {
+            'config': '<script type=\'text/javascript\' async=\'true\' src=\'http://cdn.adnxs.com/v/s/152/trk.js#v;vk=appnexus.com-omid;tv=native1-18h;dom_id=%native_dom_id%;st=0;d=1x1;vc=iab;vid_ccr=1;tag_id=13232354;cb=http%3A%2F%2Fams1-ib.adnxs.com%2Fvevent%3Freferrer%3Dhttp%253A%252F%252Ftestpages-pmahe.tp.adnxs.net%252F01_basic_single%26e%3DwqT_3QLNB6DNAwAAAwDWAAUBCLfl_-MFEMStk8u3lPTjRxih88aF0fq_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-CoAcgDANgD8ao-4AMA6AMA-AMBgAQAkgQNL3V0L3YzL3ByZWJpZJgEAKIECjEwLjIuMTIuMzioBIqpB7IEDggAEAEYACAAKAAwADgCuAQAwAQAyAQA0gQOOTMyNSNBTVMxOjQzMjDaBAIIAeAEAfAEg8u-LogFAZgFAKAF______8BAxgBwAUAyQUABQEU8D_SBQkJBQt8AAAA2AUB4AUB8AWZ9CH6BQQIABAAkAYBmAYAuAYAwQYBITAAAPA_yAYA2gYWChAAOgEAGBAAGADgBgw.%26s%3D971dce9d49b6bee447c8a58774fb30b40fe98171;ts=1551889079;cet=0;cecb=\'></script>'}
         }]
       }]
     };
@@ -606,7 +610,9 @@ describe('Unit: Prebid Module', function () {
             'trackers': [{
               'impression_urls': ['http://lax1-ib.adnxs.com/impression']
             }]
-          }
+          },
+          'viewability': {
+            'config': '<script type=\'text/javascript\' async=\'true\' src=\'http://cdn.adnxs.com/v/s/152/trk.js#v;vk=appnexus.com-omid;tv=native1-18h;dom_id=%native_dom_id%;st=0;d=1x1;vc=iab;vid_ccr=1;tag_id=13232354;cb=http%3A%2F%2Fams1-ib.adnxs.com%2Fvevent%3Freferrer%3Dhttp%253A%252F%252Ftestpages-pmahe.tp.adnxs.net%252F01_basic_single%26e%3DwqT_3QLNB6DNAwAAAwDWAAUBCLfl_-MFEMStk8u3lPTjRxih88aF0fq_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-CoAcgDANgD8ao-4AMA6AMA-AMBgAQAkgQNL3V0L3YzL3ByZWJpZJgEAKIECjEwLjIuMTIuMzioBIqpB7IEDggAEAEYACAAKAAwADgCuAQAwAQAyAQA0gQOOTMyNSNBTVMxOjQzMjDaBAIIAeAEAfAEg8u-LogFAZgFAKAF______8BAxgBwAUAyQUABQEU8D_SBQkJBQt8AAAA2AUB4AUB8AWZ9CH6BQQIABAAkAYBmAYAuAYAwQYBITAAAPA_yAYA2gYWChAAOgEAGBAAGADgBgw.%26s%3D971dce9d49b6bee447c8a58774fb30b40fe98171;ts=1551889079;cet=0;cecb=\'></script>'}
         }]
       }]
     };