diff --git a/README.md b/README.md
index f8f83e7..ddea596 100644
--- a/README.md
+++ b/README.md
@@ -54,6 +54,7 @@ _Distraction-free web editing with the same files from your CLI_
 - **Syntax highlighting** for Markdown (headers, bold, italic, code, links, lists)
 - **Text selection** with Shift+Arrow keys
 - **Undo/Redo** (Ctrl+Z/Ctrl+Y)
+- **Auto-formatting** (Ctrl+Shift+F) for clean Markdown
 - **Smart indentation** (Tab/Shift+Tab)
 - **Word jumping** (Ctrl+Arrow keys)
 - **Line operations** (join lines with backspace at start)
@@ -196,6 +197,7 @@ See [CLOUD.md](CLOUD.md) for detailed cloud documentation.
 | ------------- | --------------------------------------- |
 | **Ctrl+Z**    | Undo                                    |
 | **Ctrl+Y**    | Redo                                    |
+| **Ctrl+Shift+F** | Auto-format Markdown                 |
 | **Tab**       | Indent (2 spaces)                       |
 | **Shift+Tab** | Unindent                                |
 | **Enter**     | New line                                |
diff --git a/src/App.jsx b/src/App.jsx
index db7af76..c6e6fa3 100644
--- a/src/App.jsx
+++ b/src/App.jsx
@@ -6,6 +6,7 @@ import Editor from './components/Editor.jsx';
 import Preview from './components/Preview.jsx';
 import StatusBar from './components/StatusBar.jsx';
 import { syncFileOnSave } from './cloud/sync/syncOnSave.js';
+import { formatMarkdown } from './utils/formatMarkdown.js';
 
 export default function App({ filePath: initialFilePath, initialContent, layout: initialLayout, showPreview: initialShowPreview, config, onExit }) {
   const [filePath, setFilePath] = useState(initialFilePath);
@@ -118,6 +119,25 @@ export default function App({ filePath: initialFilePath, initialContent, layout:
     }
   }, [filePath, content, addTimeout]);
 
+  const handleFormat = useCallback(() => {
+    try {
+      const formatted = formatMarkdown(content);
+
+      if (formatted === content) {
+        setMessage('Already formatted');
+        addTimeout(() => setMessage(''), 1500);
+        return;
+      }
+
+      setContent(formatted);
+      setMessage('Formatted markdown');
+      addTimeout(() => setMessage(''), 2000);
+    } catch (error) {
+      setMessage(`Format error: ${error.message}`);
+      addTimeout(() => setMessage(''), 3000);
+    }
+  }, [content, addTimeout]);
+
   useInput((input, key) => {
     // Clear exit warning on any key press except Ctrl+X
     if (!(key.ctrl && input === 'x') && exitWarningShown) {
@@ -128,6 +148,10 @@ export default function App({ filePath: initialFilePath, initialContent, layout:
     if (key.ctrl && input === 's') {
       handleSave();
     }
+    // Ctrl+Shift+F: Format markdown
+    if (key.ctrl && key.shift && input && input.toLowerCase() === 'f') {
+      handleFormat();
+    }
     // Ctrl+O: Open config file (or return to original file if editing config)
     if (key.ctrl && input === 'o') {
       const configPath = getConfigPath();
diff --git a/src/components/TextBuffer.jsx b/src/components/TextBuffer.jsx
index 35541fe..00460ca 100644
--- a/src/components/TextBuffer.jsx
+++ b/src/components/TextBuffer.jsx
@@ -269,16 +269,49 @@ export default function TextBuffer({ content, onChange, isFocused = true, viewpo
     onChange(lines.map(l => l.text).join('\n'));
   }, [lines, onChange]);
 
-  // Reset when content prop changes (initial load only)
+  // Sync editor when parent content changes (e.g., external formatting)
   useEffect(() => {
-    if (lines.length === 0 || (lines.length === 1 && lines[0].text === '')) {
-      const newLines = content.split('\n').map((line) => ({
-        id: `line-${lineIdCounter++}`,
-        text: line
-      }));
-      setLines(newLines);
+    const currentContent = lines.map(l => l.text).join('\n');
+    if (content === currentContent) {
+      return;
     }
-  }, []);
+
+    const newLines = content.split('\n').map((line) => ({
+      id: `line-${lineIdCounter++}`,
+      text: line
+    }));
+
+    setLines(newLines);
+    setSelection(null);
+
+    const newCursorLine = Math.min(cursorLine, newLines.length - 1);
+    const newCursorCol = Math.min(newLines[newCursorLine]?.text?.length || 0, cursorCol);
+    setCursorLine(newCursorLine);
+    setCursorCol(newCursorCol);
+
+    setHistory(prevHistory => {
+      const truncated = prevHistory
+        .slice(0, historyIndex + 1)
+        .map(state => ({
+          lines: state.lines.map(l => ({ ...l })),
+          cursorLine: state.cursorLine,
+          cursorCol: state.cursorCol,
+        }));
+
+      truncated.push({
+        lines: newLines.map(l => ({ ...l })),
+        cursorLine: newCursorLine,
+        cursorCol: newCursorCol,
+      });
+
+      if (truncated.length > 100) {
+        truncated.shift();
+      }
+
+      setHistoryIndex(truncated.length - 1);
+      return truncated;
+    });
+  }, [content, cursorCol, cursorLine, historyIndex, lines]);
 
   // Keep cursor visible by adjusting scroll offset
   useEffect(() => {
diff --git a/src/utils/formatMarkdown.js b/src/utils/formatMarkdown.js
new file mode 100644
index 0000000..e7ca33d
--- /dev/null
+++ b/src/utils/formatMarkdown.js
@@ -0,0 +1,94 @@
+export function formatMarkdown(content) {
+  if (typeof content !== 'string' || content.length === 0) {
+    return '';
+  }
+
+  const normalized = content.replace(/\r\n/g, '\n').replace(/\r/g, '\n');
+  const lines = normalized.split('\n');
+  const formatted = [];
+
+  let blankLineCount = 0;
+  let inCodeFence = false;
+
+  for (let i = 0; i < lines.length; i++) {
+    const originalLine = lines[i];
+    const trimmedEnd = originalLine.replace(/\s+$/u, '');
+    const fenceMatch = trimmedEnd.trimStart().match(/^(?:```+|~~~+)(.*)$/);
+
+    if (inCodeFence) {
+      formatted.push(originalLine);
+      if (fenceMatch) {
+        inCodeFence = false;
+        blankLineCount = 0;
+      }
+      continue;
+    }
+
+    if (fenceMatch) {
+      formatted.push(trimmedEnd);
+      inCodeFence = true;
+      blankLineCount = 0;
+      continue;
+    }
+
+    if (trimmedEnd.trim() === '') {
+      if (formatted.length === 0) {
+        continue;
+      }
+      blankLineCount += 1;
+      if (blankLineCount > 1) {
+        continue;
+      }
+      formatted.push('');
+      continue;
+    }
+
+    blankLineCount = 0;
+    let processedLine = trimmedEnd;
+
+    const headingMatch = processedLine.match(/^(#{1,6})(\s*)(.*)$/);
+    if (headingMatch) {
+      const [, hashes, , text] = headingMatch;
+      const headingText = text.trim();
+      processedLine = headingText ? `${hashes} ${headingText}` : hashes;
+      formatted.push(processedLine);
+      continue;
+    }
+
+    const blockquoteMatch = processedLine.match(/^(\s*>+)(\s*)(.*)$/);
+    if (blockquoteMatch) {
+      const [, markers, , text] = blockquoteMatch;
+      const quoteText = text.replace(/^\s+/, '');
+      processedLine = quoteText ? `${markers} ${quoteText}` : markers;
+      formatted.push(processedLine);
+      continue;
+    }
+
+    const listMatch = processedLine.match(/^(\s*)(?:([-*+])|(\d+\.))(\s*)(.*)$/);
+    if (listMatch) {
+      const indent = listMatch[1] || '';
+      const bullet = listMatch[2] || listMatch[3] || '';
+      const listText = (listMatch[5] || '').replace(/^\s+/, '');
+      const spacer = listText ? ' ' : '';
+      processedLine = `${indent}${bullet}${spacer}${listText}`;
+      formatted.push(processedLine);
+      continue;
+    }
+
+    formatted.push(processedLine);
+  }
+
+  while (formatted.length > 0 && formatted[formatted.length - 1] === '') {
+    formatted.pop();
+  }
+
+  if (formatted.length === 0) {
+    return '';
+  }
+
+  let result = formatted.join('\n');
+  if (!result.endsWith('\n')) {
+    result += '\n';
+  }
+  return result;
+}
diff --git a/tests/unit/formatMarkdown.test.js b/tests/unit/formatMarkdown.test.js
new file mode 100644
index 0000000..4d76d16
--- /dev/null
+++ b/tests/unit/formatMarkdown.test.js
@@ -0,0 +1,21 @@
+import { formatMarkdown } from '../../src/utils/formatMarkdown.js';
+
+describe('formatMarkdown', () => {
+  it('normalizes headings and ensures a trailing newline', () => {
+    const input = '#Heading\n\nSome text';
+    const output = formatMarkdown(input);
+    expect(output).toBe('# Heading\n\nSome text\n');
+  });
+
+  it('collapses excessive blank lines and trims list spacing', () => {
+    const input = '-   item one\n\n\n-    item two';
+    const output = formatMarkdown(input);
+    expect(output).toBe('- item one\n\n- item two\n');
+  });
+
+  it('preserves code fences without altering inner content', () => {
+    const input = '```js\nconst value = 1;  \n```\n';
+    const output = formatMarkdown(input);
+    expect(output).toBe('```js\nconst value = 1;  \n```\n');
+  });
+});