diff --git a/demo/client/client.ts b/demo/client/client.ts
index 63da8fca..e484d8ca 100644
--- a/demo/client/client.ts
+++ b/demo/client/client.ts
@@ -19,6 +19,7 @@ import { AddonImageWindow } from './components/window/addonImageWindow';
 import { AddonSearchWindow } from './components/window/addonSearchWindow';
 import { AddonSerializeWindow } from './components/window/addonSerializeWindow';
 import { AddonsWindow } from './components/window/addonsWindow';
+import { CellInspectorWindow } from './components/window/cellInspectorWindow';
 import { ControlBar } from './components/controlBar';
 import { WebglWindow } from './components/window/webglWindow';
 import { OptionsWindow } from './components/window/optionsWindow';
@@ -206,6 +207,7 @@ if (document.location.pathname === '/test') {
   controlBar = new ControlBar(document.getElementById('sidebar'), document.querySelector('.banner-tabs'), []);
   optionsWindow = controlBar.registerWindow(new OptionsWindow(typedTerm, addons, { updateTerminalSize, updateTerminalContainerBackground }));
   const styleWindow = controlBar.registerWindow(new StyleWindow(typedTerm, addons));
+  controlBar.registerWindow(new CellInspectorWindow(typedTerm, addons));
   controlBar.registerWindow(new VtWindow(typedTerm, addons));
   addonsWindow = controlBar.registerWindow(new AddonsWindow(typedTerm, addons));
   addonSearchWindow = controlBar.registerWindow(new AddonSearchWindow(typedTerm, addons), { afterId: 'addons', hidden: true, italics: true });
diff --git a/demo/client/components/window/cellInspectorWindow.ts b/demo/client/components/window/cellInspectorWindow.ts
new file mode 100644
index 00000000..8d3b0330
--- /dev/null
+++ b/demo/client/components/window/cellInspectorWindow.ts
@@ -0,0 +1,218 @@
+/**
+ * Copyright (c) 2018 The xterm.js authors. All rights reserved.
+ * @license MIT
+ */
+
+import { BaseWindow } from './baseWindow';
+import type { IControlWindow } from '../controlBar';
+import type { Terminal, IBufferCell } from '@xterm/xterm';
+import type { AddonCollection } from '../../types';
+
+export class CellInspectorWindow extends BaseWindow implements IControlWindow {
+  public readonly id = 'cell-inspector';
+  public readonly label = 'Cell Inspector';
+
+  private _container: HTMLElement;
+  private _positionEl: HTMLElement;
+  private _charEl: HTMLElement;
+  private _codeEl: HTMLElement;
+  private _widthEl: HTMLElement;
+  private _fgEl: HTMLElement;
+  private _bgEl: HTMLElement;
+  private _attrsEl: HTMLElement;
+
+  constructor(
+    terminal: Terminal,
+    addons: AddonCollection,
+  ) {
+    super(terminal, addons);
+  }
+
+  public build(container: HTMLElement): void {
+    this._container = container;
+
+    const dl = document.createElement('dl');
+    dl.style.fontFamily = 'monospace';
+    dl.style.fontSize = '12px';
+
+    this._positionEl = this._addRow(dl, 'Position');
+    this._charEl = this._addRow(dl, 'Character');
+    this._codeEl = this._addRow(dl, 'Codepoint');
+    this._widthEl = this._addRow(dl, 'Width');
+    this._fgEl = this._addRow(dl, 'Foreground');
+    this._bgEl = this._addRow(dl, 'Background');
+    this._attrsEl = this._addRow(dl, 'Attributes');
+
+    container.appendChild(dl);
+
+    // Add mouse move listener
+    this._setupMouseListener();
+  }
+
+  private _addRow(dl: HTMLElement, label: string): HTMLElement {
+    const dt = document.createElement('dt');
+    dt.textContent = label;
+    dt.style.fontWeight = 'bold';
+    dt.style.marginTop = '4px';
+    dl.appendChild(dt);
+
+    const dd = document.createElement('dd');
+    dd.textContent = '-';
+    dd.style.margin = '0 0 0 16px';
+    dl.appendChild(dd);
+
+    return dd;
+  }
+
+  private _setupMouseListener(): void {
+    const terminal = this._terminal;
+    if (!terminal.element) {
+      return;
+    }
+
+    const cell = terminal.buffer.active.getNullCell();
+
+    terminal.element.addEventListener('mousemove', (e: MouseEvent) => {
+      const core = (terminal as any)._core;
+      const coords = core._mouseService?.getCoords(e, core.screenElement, terminal.cols, terminal.rows);
+      if (!coords) {
+        this._clearDisplay();
+        return;
+      }
+
+      const x = coords[0] - 1;
+      const y = coords[1] - 1;
+      const bufferY = terminal.buffer.active.viewportY + y;
+
+      const line = terminal.buffer.active.getLine(bufferY);
+      if (!line) {
+        this._clearDisplay();
+        return;
+      }
+
+      const cellData = line.getCell(x, cell);
+      if (!cellData) {
+        this._clearDisplay();
+        return;
+      }
+
+      this._updateDisplay(x, y, bufferY, cellData);
+    });
+
+    terminal.element.addEventListener('mouseleave', () => {
+      this._clearDisplay();
+    });
+  }
+
+  private _clearDisplay(): void {
+    this._positionEl.textContent = '-';
+    this._charEl.textContent = '-';
+    this._codeEl.textContent = '-';
+    this._widthEl.textContent = '-';
+    this._fgEl.textContent = '-';
+    this._bgEl.textContent = '-';
+    this._attrsEl.textContent = '-';
+  }
+
+  private _updateDisplay(x: number, y: number, bufferY: number, cell: IBufferCell): void {
+    // Position
+    this._positionEl.textContent = `x=${x}, y=${y} (buffer: ${bufferY})`;
+
+    // Character
+    const chars = cell.getChars();
+    this._charEl.textContent = chars.length > 0 ? `"${chars}"` : '(empty)';
+
+    // Codepoint(s)
+    if (chars.length > 0) {
+      const codepoints = [...chars].map(c => {
+        const cp = c.codePointAt(0)!;
+        return `U+${cp.toString(16).toUpperCase().padStart(4, '0')}`;
+      });
+      this._codeEl.textContent = codepoints.join(' ');
+    } else {
+      this._codeEl.textContent = '(none)';
+    }
+
+    // Width
+    this._widthEl.textContent = cell.getWidth().toString();
+
+    // Foreground color
+    this._fgEl.textContent = this._formatFgColor(
+      cell.getFgColor(),
+      cell.isFgDefault(),
+      cell.isFgPalette(),
+      cell.isFgRGB()
+    );
+
+    // Background color
+    this._bgEl.textContent = this._formatBgColor(
+      cell.getBgColor(),
+      cell.isBgDefault(),
+      cell.isBgPalette(),
+      cell.isBgRGB()
+    );
+
+    // Attributes (SGR codes)
+    const attrs: string[] = [];
+    if (cell.isBold()) attrs.push('bold (1)');
+    if (cell.isDim()) attrs.push('dim (2)');
+    if (cell.isItalic()) attrs.push('italic (3)');
+    if (cell.isUnderline()) attrs.push('underline (4)');
+    if (cell.isBlink()) attrs.push('blink (5)');
+    if (cell.isInverse()) attrs.push('inverse (7)');
+    if (cell.isInvisible()) attrs.push('invisible (8)');
+    if (cell.isStrikethrough()) attrs.push('strikethrough (9)');
+    if (cell.isOverline()) attrs.push('overline (53)');
+    this._attrsEl.textContent = attrs.length > 0 ? attrs.join(', ') : '(none)';
+  }
+
+  private _formatFgColor(color: number, isDefault: boolean, isPalette: boolean, isRGB: boolean): string {
+    if (isDefault) {
+      return 'default (39)';
+    }
+    if (isPalette) {
+      // SGR 30-37 for colors 0-7, 90-97 for colors 8-15, or 38;5;n for 0-255
+      let sgr: string;
+      if (color < 8) {
+        sgr = `${30 + color}`;
+      } else if (color < 16) {
+        sgr = `${90 + color - 8}`;
+      } else {
+        sgr = `38;5;${color}`;
+      }
+      return `palette(${color}) (${sgr})`;
+    }
+    if (isRGB) {
+      const r = (color >> 16) & 0xFF;
+      const g = (color >> 8) & 0xFF;
+      const b = color & 0xFF;
+      return `#${color.toString(16).toUpperCase().padStart(6, '0')} (38;2;${r};${g};${b})`;
+    }
+    return `unknown(${color})`;
+  }
+
+  private _formatBgColor(color: number, isDefault: boolean, isPalette: boolean, isRGB: boolean): string {
+    if (isDefault) {
+      return 'default (49)';
+    }
+    if (isPalette) {
+      // SGR 40-47 for colors 0-7, 100-107 for colors 8-15, or 48;5;n for 0-255
+      let sgr: string;
+      if (color < 8) {
+        sgr = `${40 + color}`;
+      } else if (color < 16) {
+        sgr = `${100 + color - 8}`;
+      } else {
+        sgr = `48;5;${color}`;
+      }
+      return `palette(${color}) (${sgr})`;
+    }
+    if (isRGB) {
+      const r = (color >> 16) & 0xFF;
+      const g = (color >> 8) & 0xFF;
+      const b = color & 0xFF;
+      return `#${color.toString(16).toUpperCase().padStart(6, '0')} (48;2;${r};${g};${b})`;
+    }
+    return `unknown(${color})`;
+  }
+}