diff --git a/frontend/apps/remark42/app/styles/global.css b/frontend/apps/remark42/app/styles/global.css
index d3cfd400..2b548833 100644
--- a/frontend/apps/remark42/app/styles/global.css
+++ b/frontend/apps/remark42/app/styles/global.css
@@ -2,7 +2,7 @@ body {
   -webkit-font-smoothing: antialiased;
   -moz-osx-font-smoothing: grayscale;
   margin: 0;
-  padding: 6px;
+  padding: 0;
   font-family: system-ui;
   font-size: 14px;
   color: rgb(var(--primary-text-color));
diff --git a/frontend/apps/remark42/app/utils/post-message.spec.ts b/frontend/apps/remark42/app/utils/post-message.spec.ts
new file mode 100644
index 00000000..9d200011
--- /dev/null
+++ b/frontend/apps/remark42/app/utils/post-message.spec.ts
@@ -0,0 +1,54 @@
+import { updateIframeHeight } from './post-message';
+
+describe('updateIframeHeight', () => {
+  const postMessage = jest.fn();
+  let originalParent: Window;
+
+  beforeAll(() => {
+    originalParent = window.parent;
+    // postMessageToParent bails out when window.parent is window, which is the case in jsdom
+    Object.defineProperty(window, 'parent', { value: { postMessage }, writable: true, configurable: true });
+  });
+
+  afterAll(() => {
+    Object.defineProperty(window, 'parent', { value: originalParent, writable: true, configurable: true });
+  });
+
+  beforeEach(() => {
+    postMessage.mockClear();
+    jest.spyOn(document.body, 'offsetHeight', 'get').mockReturnValue(500);
+  });
+
+  afterEach(() => {
+    jest.restoreAllMocks();
+  });
+
+  it('should report the document height without adding to it', () => {
+    updateIframeHeight();
+
+    expect(postMessage).toHaveBeenCalledWith({ height: 500 }, '*');
+  });
+
+  it('should report the dropdown height when it exceeds the document height', () => {
+    const dropdown = document.createElement('div');
+
+    jest.spyOn(dropdown, 'getBoundingClientRect').mockReturnValue({ top: 100 } as DOMRect);
+    jest.spyOn(dropdown, 'scrollHeight', 'get').mockReturnValue(600);
+
+    updateIframeHeight(dropdown);
+
+    // 20px allowance for the shadow under the dropdown
+    expect(postMessage).toHaveBeenCalledWith({ height: 720 }, '*');
+  });
+
+  it('should report the document height when it exceeds the dropdown height', () => {
+    const dropdown = document.createElement('div');
+
+    jest.spyOn(dropdown, 'getBoundingClientRect').mockReturnValue({ top: 10 } as DOMRect);
+    jest.spyOn(dropdown, 'scrollHeight', 'get').mockReturnValue(50);
+
+    updateIframeHeight(dropdown);
+
+    expect(postMessage).toHaveBeenCalledWith({ height: 500 }, '*');
+  });
+});
diff --git a/frontend/apps/remark42/app/utils/post-message.ts b/frontend/apps/remark42/app/utils/post-message.ts
index 3ec62ad3..bee61e21 100644
--- a/frontend/apps/remark42/app/utils/post-message.ts
+++ b/frontend/apps/remark42/app/utils/post-message.ts
@@ -78,8 +78,8 @@ export function updateIframeHeight(dropdown?: HTMLElement) {
     scrollHeight = window.scrollY + Math.abs(top) + dropdown.scrollHeight + 20;
   }
 
-  // The size of vertical padding on body is 12px
-  const bodyHeight = document.body.offsetHeight + 12;
+  // offsetHeight already covers padding and border, so it is the full document height
+  const bodyHeight = document.body.offsetHeight;
 
   postMessageToParent({ height: Math.max(scrollHeight, bodyHeight) });
 }