diff --git a/src/lib/editor/tableFormatterPlugin.ts b/src/lib/editor/tableFormatterPlugin.ts
new file mode 100644
index 0000000..bf4eeb0
--- /dev/null
+++ b/src/lib/editor/tableFormatterPlugin.ts
@@ -0,0 +1,148 @@
+import { ViewPlugin, ViewUpdate, EditorView } from '@codemirror/view';
+import { syntaxTree } from '@codemirror/language';
+
+// Helper to count CJK chars as 2 for better alignment
+function getDisplayLength(str: string): number {
+	let len = 0;
+	for (let i = 0; i < str.length; i++) {
+		len += str.charCodeAt(i) > 255 ? 2 : 1;
+	}
+	return len;
+}
+
+function padEnd(str: string, targetLength: number): string {
+	const curLen = getDisplayLength(str);
+	if (curLen >= targetLength) return str;
+	return str + ' '.repeat(targetLength - curLen);
+}
+
+export function formatMarkdownTable(tableStr: string): string {
+	const lines = tableStr.trim().split('\n');
+	if (lines.length < 2) return tableStr; // Not a valid table
+
+	const rows = lines.map((line) => {
+		const content = line.trim();
+		const cols = content.split('|');
+		// Remove empty outer columns if they exist
+		if (cols.length > 0 && cols[0].trim() === '') cols.shift();
+		if (cols.length > 0 && cols[cols.length - 1].trim() === '') cols.pop();
+		return cols.map((c) => c.trim());
+	});
+
+	const colWidths: number[] = [];
+	rows.forEach((row) => {
+		row.forEach((col, i) => {
+			const len = getDisplayLength(col);
+			if (!colWidths[i] || len > colWidths[i]) {
+				colWidths[i] = len;
+			}
+		});
+	});
+
+	// Make sure second row (separator) has minimum width of 3 (---)
+	colWidths.forEach((w, i) => {
+		if (w < 3) colWidths[i] = 3;
+	});
+
+	const formattedLines = rows.map((row, rIndex) => {
+		if (rIndex === 1) {
+			// separator row
+			const parts = colWidths.map((w, i) => {
+				const col = row[i] || '';
+				const leftAlign = col.startsWith(':');
+				const rightAlign = col.endsWith(':');
+				let sep = '-'.repeat(w);
+				if (leftAlign && rightAlign) {
+					sep = ':' + '-'.repeat(w - 2) + ':';
+				} else if (leftAlign) {
+					sep = ':' + '-'.repeat(w - 1);
+				} else if (rightAlign) {
+					sep = '-'.repeat(w - 1) + ':';
+				}
+				return sep;
+			});
+			return '| ' + parts.join(' | ') + ' |';
+		} else {
+			const parts = colWidths.map((w, i) => {
+				const col = row[i] || '';
+				return padEnd(col, w);
+			});
+			return '| ' + parts.join(' | ') + ' |';
+		}
+	});
+
+	return formattedLines.join('\n');
+}
+
+export const tableFormatterPlugin = ViewPlugin.fromClass(
+	class {
+		lastTableRange: any = null;
+
+		constructor(view: EditorView) {
+			this.lastTableRange = this.getCurrentTableRange(view);
+		}
+
+		update(update: ViewUpdate) {
+			if (update.selectionSet || update.docChanged || update.focusChanged) {
+				const view = update.view;
+
+				const currentTableRange: { from: number; to: number } | null =
+					this.getCurrentTableRange(view);
+				const focusLost = !view.hasFocus;
+				const movedOutOfTable =
+					this.lastTableRange &&
+					(!currentTableRange || currentTableRange.from !== this.lastTableRange.from);
+
+				// Trigger format if focus is lost or moved out of the table
+				if (this.lastTableRange && (focusLost || movedOutOfTable)) {
+					this.formatTable(view, this.lastTableRange);
+				}
+
+				if (!focusLost) {
+					this.lastTableRange = currentTableRange;
+				} else {
+					this.lastTableRange = null;
+				}
+			}
+		}
+
+		getCurrentTableRange(view: EditorView) {
+			const state = view.state;
+			const pos = state.selection.main.head;
+			const tree = syntaxTree(state);
+			let tableRange: any = null;
+
+			tree.iterate({
+				from: pos,
+				to: pos,
+				enter: (node: any) => {
+					if (node.name === 'Table') {
+						tableRange = { from: node.from, to: node.to };
+						return false; // stop iteration
+					}
+				}
+			});
+			return tableRange;
+		}
+
+		formatTable(view: EditorView, range: { from: number; to: number }) {
+			const state = view.state;
+			// check if valid range
+			if (range.to > state.doc.length) return;
+
+			const tableStr = state.doc.sliceString(range.from, range.to);
+			// sanity check
+			if (!tableStr.trim().startsWith('|')) return;
+
+			const formatted = formatMarkdownTable(tableStr);
+			if (formatted !== tableStr) {
+				// We schedule the dispatch in the next microtask to avoid updating during update
+				Promise.resolve().then(() => {
+					view.dispatch({
+						changes: { from: range.from, to: range.to, insert: formatted }
+					});
+				});
+			}
+		}
+	}
+);