diff --git a/modules/33acrossBidAdapter.js b/modules/33acrossBidAdapter.js
index 801a5d564a3..f53bf8b9d17 100644
--- a/modules/33acrossBidAdapter.js
+++ b/modules/33acrossBidAdapter.js
@@ -64,7 +64,7 @@ function _getAdSlotHTMLElement(adUnitCode) {
 
 // Infer the necessary data from valid bid for a minimal ttxRequest and create HTTP request
 // NOTE: At this point, TTX only accepts request for a single impression
-function _createServerRequest(bidRequest, gdprConsent) {
+function _createServerRequest(bidRequest, gdprConsent = {}) {
   const ttxRequest = {};
   const params = bidRequest.params;
   const element = _getAdSlotHTMLElement(bidRequest.adUnitCode);
@@ -143,14 +143,22 @@ function _createServerRequest(bidRequest, gdprConsent) {
 }
 
 // Sync object will always be of type iframe for TTX
-function _createSync(siteId) {
+function _createSync({siteId, gdprConsent = {}}) {
   const ttxSettings = config.getConfig('ttxSettings');
   const syncUrl = (ttxSettings && ttxSettings.syncUrl) || SYNC_ENDPOINT;
 
-  return {
+  const {consentString, gdprApplies} = gdprConsent;
+
+  const sync = {
     type: 'iframe',
-    url: `${syncUrl}&id=${siteId}`
+    url: `${syncUrl}&id=${siteId}&gdpr_consent=${encodeURIComponent(consentString)}`
+  };
+
+  if (typeof gdprApplies === 'boolean') {
+    sync.url += `&gdpr=${Number(gdprApplies)}`;
   }
+
+  return sync;
 }
 
 function _getSize(size) {
@@ -282,8 +290,6 @@ function isBidRequestValid(bid) {
 
 // NOTE: With regards to gdrp consent data,
 // - the server independently infers gdpr applicability therefore, setting the default value to false
-// - the server, at this point, also doesn't need the consent string to handle gdpr compliance. So passing
-//    value whether set or not, for the sake of future dev.
 function buildRequests(bidRequests, bidderRequest) {
   const gdprConsent = Object.assign({
     consentString: undefined,
@@ -307,14 +313,12 @@ function interpretResponse(serverResponse, bidRequest) {
   return bidResponses;
 }
 
-// Register one sync per unique guid
-// NOTE: If gdpr applies do not sync
+// Register one sync per unique guid so long as iframe is enable
+// Else no syncs
+// For logic on how we handle gdpr data see _createSyncs and module's unit tests
+// '33acrossBidAdapter#getUserSyncs'
 function getUserSyncs(syncOptions, responses, gdprConsent) {
-  if (gdprConsent && gdprConsent.gdprApplies === true) {
-    return []
-  } else {
-    return (syncOptions.iframeEnabled) ? adapterState.uniqueSiteIds.map(_createSync) : ([]);
-  }
+  return (syncOptions.iframeEnabled) ? adapterState.uniqueSiteIds.map((siteId) => _createSync({gdprConsent, siteId})) : ([]);
 }
 
 export const spec = {
diff --git a/modules/33acrossBidAdapter.md b/modules/33acrossBidAdapter.md
index 58e3b2b273a..c313f3b6e0b 100644
--- a/modules/33acrossBidAdapter.md
+++ b/modules/33acrossBidAdapter.md
@@ -24,7 +24,7 @@ var adUnits = [
     bids: [{
         bidder: '33across',
         params: {
-            siteId: 'examplePub1234',     
+            siteId: 'cxBE0qjUir6iopaKkGJozW',     
             productId: 'siab'     
         }
     }]
diff --git a/test/spec/modules/33acrossBidAdapter_spec.js b/test/spec/modules/33acrossBidAdapter_spec.js
index 7e1a8619c63..08ea0a863ee 100644
--- a/test/spec/modules/33acrossBidAdapter_spec.js
+++ b/test/spec/modules/33acrossBidAdapter_spec.js
@@ -618,73 +618,140 @@ describe('33acrossBidAdapter:', function () {
       ];
     });
 
-    context('when gdpr does not apply', function() {
-      let gdprConsent;
+    context('when iframe is not enabled', function() {
+      it('returns empty sync array', function() {
+        const syncOptions = {};
+
+        spec.buildRequests(bidRequests);
+
+        expect(spec.getUserSyncs(syncOptions)).to.deep.equal([]);
+      });
+    });
 
+    context('when iframe is enabled', function() {
+      let syncOptions;
       beforeEach(function() {
-        gdprConsent = {
-          gdprApplies: false
+        syncOptions = {
+          iframeEnabled: true
         };
       });
 
-      context('when iframe is not enabled', function() {
-        it('returns empty sync array', function() {
-          const syncOptions = {};
+      context('when there is no gdpr consent data', function() {
+        it('returns sync urls with undefined consent string as param', function() {
+          spec.buildRequests(bidRequests);
+
+          const syncResults = spec.getUserSyncs(syncOptions, {}, undefined);
+          const expectedSyncs = [
+            {
+              type: 'iframe',
+              url: `${syncs[0].url}&gdpr_consent=undefined`
+            },
+            {
+              type: 'iframe',
+              url: `${syncs[1].url}&gdpr_consent=undefined`
+            }
+          ]
+
+          expect(syncResults).to.deep.equal(expectedSyncs);
+        })
+      });
 
+      context('when gdpr applies but there is no consent string', function() {
+        it('returns sync urls with undefined consent string as param and gdpr=1', function() {
           spec.buildRequests(bidRequests);
 
-          expect(spec.getUserSyncs(syncOptions, {}, gdprConsent)).to.deep.equal([]);
+          const syncResults = spec.getUserSyncs(syncOptions, {}, {gdprApplies: true});
+          const expectedSyncs = [
+            {
+              type: 'iframe',
+              url: `${syncs[0].url}&gdpr_consent=undefined&gdpr=1`
+            },
+            {
+              type: 'iframe',
+              url: `${syncs[1].url}&gdpr_consent=undefined&gdpr=1`
+            }
+          ];
+
+          expect(syncResults).to.deep.equal(expectedSyncs);
         });
       });
 
-      context('when iframe is enabled', function() {
-        it('returns sync array equal to number of unique siteIDs', function() {
-          const syncOptions = {
-            iframeEnabled: true
-          };
-
+      context('when gdpr applies and there is consent string', function() {
+        it('returns sync urls with gdpr_consent=consent string as param and gdpr=1', function() {
           spec.buildRequests(bidRequests);
 
-          expect(spec.getUserSyncs(syncOptions, {}, gdprConsent)).to.deep.equal(syncs);
+          const syncResults = spec.getUserSyncs(syncOptions, {}, {gdprApplies: true, consentString: 'consent123A'});
+          const expectedSyncs = [
+            {
+              type: 'iframe',
+              url: `${syncs[0].url}&gdpr_consent=consent123A&gdpr=1`
+            },
+            {
+              type: 'iframe',
+              url: `${syncs[1].url}&gdpr_consent=consent123A&gdpr=1`
+            }
+          ];
+
+          expect(syncResults).to.deep.equal(expectedSyncs);
         });
       });
-    });
-
-    context('when consent data is not defined', function() {
-      context('when iframe is not enabled', function() {
-        it('returns empty sync array', function() {
-          const syncOptions = {};
 
+      context('when gdpr does not apply and there is no consent string', function() {
+        it('returns sync urls with undefined consent string as param and gdpr=0', function() {
           spec.buildRequests(bidRequests);
 
-          expect(spec.getUserSyncs(syncOptions)).to.deep.equal([]);
+          const syncResults = spec.getUserSyncs(syncOptions, {}, {gdprApplies: false});
+          const expectedSyncs = [
+            {
+              type: 'iframe',
+              url: `${syncs[0].url}&gdpr_consent=undefined&gdpr=0`
+            },
+            {
+              type: 'iframe',
+              url: `${syncs[1].url}&gdpr_consent=undefined&gdpr=0`
+            }
+          ];
+          expect(syncResults).to.deep.equal(expectedSyncs);
         });
       });
 
-      context('when iframe is enabled', function() {
-        it('returns sync array equal to number of unique siteIDs', function() {
-          const syncOptions = {
-            iframeEnabled: true
-          };
-
+      context('when gdpr is unknown and there is consent string', function() {
+        it('returns sync urls with only consent string as param', function() {
           spec.buildRequests(bidRequests);
 
-          expect(spec.getUserSyncs(syncOptions)).to.deep.equal(syncs);
+          const syncResults = spec.getUserSyncs(syncOptions, {}, {consentString: 'consent123A'});
+          const expectedSyncs = [
+            {
+              type: 'iframe',
+              url: `${syncs[0].url}&gdpr_consent=consent123A`
+            },
+            {
+              type: 'iframe',
+              url: `${syncs[1].url}&gdpr_consent=consent123A`
+            }
+          ];
+          expect(syncResults).to.deep.equal(expectedSyncs);
         });
       });
-    });
 
-    context('when gdpr applies', function() {
-      it('returns empty sync array', function() {
-        const syncOptions = {};
-        const gdprConsent = {
-          gdprApplies: true
-        };
-
-        spec.buildRequests(bidRequests);
+      context('when gdpr does not apply and there is consent string (yikes!)', function() {
+        it('returns sync urls with consent string as param and gdpr=0', function() {
+          spec.buildRequests(bidRequests);
 
-        expect(spec.getUserSyncs(syncOptions, {}, gdprConsent)).to.deep.equal([]);
+          const syncResults = spec.getUserSyncs(syncOptions, {}, {gdprApplies: false, consentString: 'consent123A'});
+          const expectedSyncs = [
+            {
+              type: 'iframe',
+              url: `${syncs[0].url}&gdpr_consent=consent123A&gdpr=0`
+            },
+            {
+              type: 'iframe',
+              url: `${syncs[1].url}&gdpr_consent=consent123A&gdpr=0`
+            }
+          ];
+          expect(syncResults).to.deep.equal(expectedSyncs);
+        });
       });
-    })
+    });
   });
 });