diff --git a/libraries/tracker-core/src/emitter/emitter_request.ts b/libraries/tracker-core/src/emitter/emitter_request.ts
index 4717ad02e..c5b1b19a7 100644
--- a/libraries/tracker-core/src/emitter/emitter_request.ts
+++ b/libraries/tracker-core/src/emitter/emitter_request.ts
@@ -33,9 +33,12 @@ export interface EmitterRequest {
    */
   countEvents: () => number;
   /**
-   * Cancel the timeout timer, should be called when the request is sent
+   * Cancel timeout timer if it is still pending.
+   * If not successful, the request will be aborted.
+   * @param successful - Whether the request was successful
+   * @param reason - Reason for aborting the request
    */
-  cancelTimeoutTimer: () => void;
+  closeRequest: (successful: boolean, reason?: string) => void;
 }
 
 export interface EmitterRequestConfiguration {
@@ -48,7 +51,6 @@ export interface EmitterRequestConfiguration {
   keepalive?: boolean;
   postPath?: string;
   useStm?: boolean;
-  bufferSize?: number;
   maxPostBytes?: number,
   credentials?: 'omit' | 'same-origin' | 'include';
 }
@@ -89,19 +91,23 @@ export function newEmitterRequest({
   keepalive = true,
   postPath = '/com.snowplowanalytics.snowplow/tp2',
   useStm = true,
-  bufferSize,
   maxPostBytes = 40000,
   credentials = 'include',
 }: EmitterRequestConfiguration): EmitterRequest {
   let events: EmitterEvent[] = [];
   let usePost = eventMethod.toLowerCase() === 'post';
   let timer: ReturnType<typeof setTimeout> | undefined;
+  let abortController: AbortController | undefined;
 
   function countBytes(): number {
-    return events.reduce(
+    let count = events.reduce(
       (acc, event) => acc + (usePost ? event.getPOSTRequestBytesCount() : event.getGETRequestBytesCount()),
       0
     );
+    if (usePost) {
+      count += 88; // 88 bytes for the payload_data envelope
+    }
+    return count;
   }
 
   function countEvents(): number {
@@ -112,7 +118,6 @@ export function newEmitterRequest({
     return events.length > 0 ? events[0].getServerAnonymization() : undefined;
   }
 
-
   function addEvent(event: EmitterEvent) {
     if (events.length > 0 && getServerAnonymizationOfExistingEvents() !== event.getServerAnonymization()) {
       return false;
@@ -128,9 +133,6 @@ export function newEmitterRequest({
 
   function isFull(): boolean {
     if (usePost) {
-      if (bufferSize !== undefined && countEvents() >= Math.max(1, bufferSize)) {
-        return true;
-      }
       return countBytes() >= maxPostBytes;
     } else {
       return events.length >= 1;
@@ -167,15 +169,19 @@ export function newEmitterRequest({
   }
 
   function makeRequest(url: string, options: RequestInit): Request {
-    const controller = new AbortController();
+    closeRequest(false);
+
+    abortController = new AbortController();
     timer = setTimeout(() => {
-      console.error('Request timed out');
-      controller.abort()
+      const reason = 'Request timed out';
+      console.error(reason);
+      timer = undefined;
+      closeRequest(false, reason);
     }, connectionTimeout ?? 5000);
 
     const requestOptions: RequestInit = {
       headers: createHeaders(),
-      signal: controller.signal,
+      signal: abortController.signal,
       keepalive,
       credentials,
       ...options,
@@ -218,11 +224,19 @@ export function newEmitterRequest({
     }
   }
 
-  function cancelTimeoutTimer() {
-    if (timer) {
+  function closeRequest(successful: boolean, reason?: string) {
+    if (timer !== undefined) {
       clearTimeout(timer);
       timer = undefined;
     }
+
+    if (abortController !== undefined) {
+      const controller = abortController;
+      abortController = undefined;
+      if (!successful) {
+        controller.abort(reason);
+      }
+    }
   }
 
   return {
@@ -232,6 +246,6 @@ export function newEmitterRequest({
     countBytes,
     countEvents,
     isFull,
-    cancelTimeoutTimer,
+    closeRequest,
   };
 }
diff --git a/libraries/tracker-core/src/emitter/index.ts b/libraries/tracker-core/src/emitter/index.ts
index 445513fc8..c22bd849b 100644
--- a/libraries/tracker-core/src/emitter/index.ts
+++ b/libraries/tracker-core/src/emitter/index.ts
@@ -47,6 +47,7 @@ export interface EmitterConfigurationBase {
   bufferSize?: number;
   /**
    * The max size a POST request can be before the tracker will force send it
+   * Also dictates the max size of a POST request before a batch of events is split into multiple requests
    * @defaultValue 40000
    */
   maxPostBytes?: number;
@@ -274,7 +275,7 @@ export function newEmitter({
     try {
       const response = await customFetch(fetchRequest);
 
-      request.cancelTimeoutTimer();
+      request.closeRequest(true);
 
       if (response.ok) {
         callOnRequestSuccess(payloads, response);
@@ -293,6 +294,8 @@ export function newEmitter({
         return { success: false, retry: willRetry, status: response.status };
       }
     } catch (e) {
+      request.closeRequest(false);
+
       const message = typeof e === 'string' ? e : e ? (e as Error).message : 'Unknown error';
       callOnRequestFailure({
         events: payloads,
@@ -312,7 +315,6 @@ export function newEmitter({
       customHeaders,
       connectionTimeout,
       keepalive,
-      bufferSize,
       maxPostBytes,
       useStm,
       credentials,
@@ -324,7 +326,7 @@ export function newEmitter({
       LOG.warn('Event (' + bytes + 'B) too big, max is ' + maxBytes);
 
     if (usePost) {
-      const bytes = emitterEvent.getPOSTRequestBytesCount();
+      const bytes = emitterEvent.getPOSTRequestBytesCount() + 88; // 88 bytes for the payload_data envelope
       const tooBig = bytes > maxPostBytes;
       if (tooBig) {
         eventTooBigWarning(bytes, maxPostBytes);
diff --git a/libraries/tracker-core/test/emitter/emitter_request.test.ts b/libraries/tracker-core/test/emitter/emitter_request.test.ts
index 264bdc30c..05342b931 100644
--- a/libraries/tracker-core/test/emitter/emitter_request.test.ts
+++ b/libraries/tracker-core/test/emitter/emitter_request.test.ts
@@ -6,7 +6,7 @@ import { newEventStorePayload } from '../../src/event_store_payload';
 
 const newEmitterEventFromPayload = (payload: Record<string, unknown>) => {
   return newEmitterEvent(newEventStorePayload({ payload }));
-}
+};
 
 // MARK: - addEvent
 
@@ -71,7 +71,7 @@ test('countBytes returns the correct byte count', (t) => {
 
   t.true(request.addEvent(newEmitterEventFromPayload({ e: 'pv', p: 'web' })));
   t.true(request.addEvent(newEmitterEventFromPayload({ e: 'pv', p: 'mob' })));
-  t.is(request.countBytes(), 40);
+  t.is(request.countBytes(), 40 + 88); // 40 bytes for each event, 88 bytes for the payload_data envelope
 });
 
 // MARK: - countEvents
@@ -89,34 +89,31 @@ test('countEvents returns the correct event count', (t) => {
 
 // MARK: - isFull
 
-test('isFull returns false when not reached buffer size', (t) => {
+test('isFull returns false when not reached max post bytes', (t) => {
   const request = newEmitterRequest({
     endpoint: 'https://example.com',
     maxPostBytes: 1000,
-    bufferSize: 2,
   });
 
   t.true(request.addEvent(newEmitterEventFromPayload({ e: 'pv', p: 'web' })));
   t.false(request.isFull());
 });
 
-test('isFull returns true when reached buffer size', (t) => {
+test('isFull returns false when reached buffer size and not max post bytes', (t) => {
   const request = newEmitterRequest({
     endpoint: 'https://example.com',
     maxPostBytes: 1000,
-    bufferSize: 2,
   });
 
   t.true(request.addEvent(newEmitterEventFromPayload({ e: 'pv', p: 'web' })));
   t.true(request.addEvent(newEmitterEventFromPayload({ e: 'pv', p: 'mob' })));
-  t.true(request.isFull());
+  t.false(request.isFull());
 });
 
 test('isFull returns true when reached max post bytes', (t) => {
   const request = newEmitterRequest({
     endpoint: 'https://example.com',
     maxPostBytes: 10,
-    bufferSize: 2,
   });
 
   t.true(request.addEvent(newEmitterEventFromPayload({ e: 'pv', p: 'web' })));
diff --git a/libraries/tracker-core/test/emitter/index.test.ts b/libraries/tracker-core/test/emitter/index.test.ts
index 05a830bb0..6e01b131a 100644
--- a/libraries/tracker-core/test/emitter/index.test.ts
+++ b/libraries/tracker-core/test/emitter/index.test.ts
@@ -311,8 +311,9 @@ test('adds a timeout to the request', async (t) => {
 
     return new Promise((resolve, reject) => {
       let timer = setTimeout(() => {
+        t.fail('Request should have timed out');
         resolve(new Response(null, { status: 200 }));
-      }, 1000);
+      }, 500);
 
       input.signal?.addEventListener('abort', () => {
         clearTimeout(timer);
diff --git a/plugins/browser-plugin-media-tracking/tests/test.test.ts b/plugins/browser-plugin-media-tracking/tests/test.test.ts
index 9176fe1ee..a1b7e2898 100644
--- a/plugins/browser-plugin-media-tracking/tests/test.test.ts
+++ b/plugins/browser-plugin-media-tracking/tests/test.test.ts
@@ -62,6 +62,7 @@ describe('MediaTrackingPlugin', () => {
         },
       ],
       contexts: { webPage: false },
+      customFetch: async () => new Response(null, { status: 200 }),
     });
     id = `media-${idx}`;
   });
diff --git a/plugins/browser-plugin-media/test/api.test.ts b/plugins/browser-plugin-media/test/api.test.ts
index 1c9910256..2229243b9 100644
--- a/plugins/browser-plugin-media/test/api.test.ts
+++ b/plugins/browser-plugin-media/test/api.test.ts
@@ -57,6 +57,7 @@ describe('Media Tracking API', () => {
         },
       ],
       contexts: { webPage: false },
+      customFetch: async () => new Response(null, { status: 200 }),
     });
     id = `media-${idx}`;
   });
diff --git a/trackers/node-tracker/test/tracker.ts b/trackers/node-tracker/test/tracker.ts
index 6d7e93115..1783eb85f 100644
--- a/trackers/node-tracker/test/tracker.ts
+++ b/trackers/node-tracker/test/tracker.ts
@@ -250,11 +250,13 @@ for (const eventMethod of testMethods) {
             eventMethod,
             bufferSize: 0,
             onRequestSuccess: (batch) => {
-              const expected = batch[0]['e'] === 'tr' ? expectedTransaction : expectedItem;
+              batch.forEach((payload) => {
+                const expected = payload['e'] === 'tr' ? expectedTransaction : expectedItem;
 
-              checkPayload(batch[0], expected, t);
+                checkPayload(payload, expected, t);
 
-              requestCount--;
+                requestCount--;
+              });
               if (requestCount === 0) {
                 resolve(batch);
               }
@@ -478,11 +480,13 @@ for (const eventMethod of testMethods) {
         endpoint,
         eventMethod,
         bufferSize: 0,
-        onRequestSuccess: ([pl]) => {
-          checkPayload(pl, expected, t);
-          count--;
+        onRequestSuccess: (batch) => {
+          batch.forEach((pl) => {
+            checkPayload(pl, expected, t);
+            count--;
+          });
           if (count === 0) {
-            resolve(pl);
+            resolve(batch);
           }
         },
         onRequestFailure: reject,