diff --git a/ts_web/elements/viewer.ts b/ts_web/elements/viewer.ts
index 0bfdb65..56ad083 100644
--- a/ts_web/elements/viewer.ts
+++ b/ts_web/elements/viewer.ts
@@ -12,6 +12,7 @@ import {
 } from "@design.estate/dees-element";
 import { demoFunc } from "./viewer.demo.js";
 import { DeDocument } from "./document.js";
+import "./page.js"; // Import DePage for thumbnail rendering
 
 import "@design.estate/dees-catalog";
 
@@ -91,6 +92,19 @@ export class DeDocumentViewer extends DeesElement {
   @state()
   accessor currentPageDisplay: string = "1 / 1";
 
+  // Sidebar state
+  @state()
+  accessor showThumbnails: boolean = true;
+
+  @state()
+  accessor sidebarWidth: number = 140;
+
+  @state()
+  accessor isResizingSidebar: boolean = false;
+
+  @state()
+  accessor thumbnailPages: number[] = [];
+
   public static styles = [
     cssManager.defaultStyles,
     css`
@@ -107,6 +121,124 @@ export class DeDocumentViewer extends DeesElement {
         --dropdown-shadow: ${cssManager.bdTheme("0 4px 16px rgba(0,0,0,0.15)", "0 4px 16px rgba(0,0,0,0.4)")};
         --slider-track: ${cssManager.bdTheme("#ddd", "#444")};
         --slider-fill: ${cssManager.bdTheme("#0066cc", "#4d9fff")};
+        --sidebar-min-width: 100px;
+        --sidebar-max-width: 300px;
+      }
+
+      /* Sidebar Styles */
+      .sidebar {
+        position: absolute;
+        left: 0;
+        top: var(--toolbar-height);
+        bottom: 0;
+        background: var(--toolbar-bg);
+        backdrop-filter: blur(12px);
+        -webkit-backdrop-filter: blur(12px);
+        border-right: 1px solid var(--toolbar-border);
+        display: flex;
+        flex-direction: column;
+        z-index: 50;
+        box-sizing: border-box;
+      }
+
+      .sidebar--collapsed {
+        width: 0 !important;
+        overflow: hidden;
+        border-right: none;
+      }
+
+      .sidebar--resizing {
+        transition: none !important;
+        user-select: none;
+      }
+
+      .sidebar__header {
+        padding: 10px 12px;
+        font-size: 11px;
+        font-weight: 600;
+        color: var(--text-secondary);
+        border-bottom: 1px solid var(--toolbar-border);
+        text-transform: uppercase;
+        letter-spacing: 0.5px;
+        flex-shrink: 0;
+      }
+
+      .sidebar__thumbnails {
+        flex: 1;
+        overflow-y: auto;
+        overflow-x: hidden;
+        padding: 8px;
+        display: flex;
+        flex-direction: column;
+        gap: 12px;
+      }
+
+      .thumbnail {
+        display: flex;
+        flex-direction: column;
+        align-items: center;
+        gap: 4px;
+        cursor: pointer;
+        padding: 4px;
+        border-radius: 6px;
+        transition: background 0.15s ease;
+        flex-shrink: 0;
+      }
+
+      .thumbnail:hover {
+        background: var(--button-hover);
+      }
+
+      .thumbnail--active {
+        background: var(--button-active);
+      }
+
+      .thumbnail--active .thumbnail__preview {
+        outline: 2px solid var(--accent-color);
+        outline-offset: 2px;
+      }
+
+      .thumbnail__preview {
+        width: 100%;
+        aspect-ratio: 210 / 297;
+        background: ${cssManager.bdTheme("#fff", "#2a2a2a")};
+        box-shadow: ${cssManager.bdTheme("0 1px 4px rgba(0,0,0,0.15)", "0 1px 4px rgba(0,0,0,0.4)")};
+        border-radius: 2px;
+        overflow: hidden;
+        position: relative;
+      }
+
+      .thumbnail__label {
+        font-size: 11px;
+        color: var(--text-secondary);
+        font-weight: 500;
+      }
+
+      .sidebar__resize-handle {
+        position: absolute;
+        top: 0;
+        right: -4px;
+        bottom: 0;
+        width: 8px;
+        cursor: ew-resize;
+        background: transparent;
+        z-index: 60;
+      }
+
+      .sidebar__resize-handle::after {
+        content: '';
+        position: absolute;
+        top: 0;
+        left: 3px;
+        bottom: 0;
+        width: 2px;
+        background: transparent;
+        transition: background 0.15s ease;
+      }
+
+      .sidebar__resize-handle:hover::after,
+      .sidebar--resizing .sidebar__resize-handle::after {
+        background: var(--accent-color);
       }
 
       .maincontainer {
@@ -413,6 +545,11 @@ export class DeDocumentViewer extends DeesElement {
         overflow-y: scroll;
         overflow-x: auto;
         overscroll-behavior: contain;
+        transition: left 0.2s ease;
+      }
+
+      .viewport--with-sidebar {
+        left: var(--current-sidebar-width, 140px);
       }
 
       .viewport--centered {
@@ -429,6 +566,16 @@ export class DeDocumentViewer extends DeesElement {
       .spacing-slider-container {
         display: none;
       }
+      /* Collapse sidebar by default on tablet */
+      .sidebar {
+        width: 0 !important;
+      }
+      .sidebar--collapsed {
+        width: 0 !important;
+      }
+      .viewport--with-sidebar {
+        left: 0 !important;
+      }
     `),
     // Phone styles
     cssManager.cssForPhone(css`
@@ -453,13 +600,30 @@ export class DeDocumentViewer extends DeesElement {
       .controls__section {
         gap: 2px;
       }
+      /* Hide sidebar and toggle on phone */
+      .sidebar {
+        display: none !important;
+      }
+      .sidebar-toggle {
+        display: none !important;
+      }
+      .viewport--with-sidebar {
+        left: 0 !important;
+      }
     `),
   ];
 
   public render(): TemplateResult {
+    const viewportClasses = [
+      "viewport",
+      this.zoomMode !== "auto" ? "viewport--centered" : "",
+      this.showThumbnails ? "viewport--with-sidebar" : "",
+    ].filter(Boolean).join(" ");
+
     return html`
-      <div class="maincontainer">
-        <div class="viewport ${this.zoomMode !== "auto" ? "viewport--centered" : ""}">
+      <div class="maincontainer" style="--current-sidebar-width: ${this.sidebarWidth}px;">
+        ${this.renderSidebar()}
+        <div class="${viewportClasses}">
           ${this.letterData
             ? html`
                 <dedocument-dedocument
@@ -480,9 +644,77 @@ export class DeDocumentViewer extends DeesElement {
     `;
   }
 
+  private renderSidebar(): TemplateResult {
+    const sidebarClasses = [
+      "sidebar",
+      !this.showThumbnails ? "sidebar--collapsed" : "",
+      this.isResizingSidebar ? "sidebar--resizing" : "",
+    ].filter(Boolean).join(" ");
+
+    const thumbnailScale = this.getThumbnailScale();
+    const currentPage = this.getCurrentPage();
+
+    return html`
+      <div class="${sidebarClasses}" style="width: ${this.sidebarWidth}px;">
+        <div class="sidebar__header">Pages</div>
+        <div class="sidebar__thumbnails">
+          ${this.thumbnailPages.map(
+            (_, i) => html`
+              <div
+                class="thumbnail ${currentPage === i + 1 ? "thumbnail--active" : ""}"
+                @click=${() => this.scrollToPage(i + 1)}
+              >
+                <div
+                  class="thumbnail__preview"
+                  style="--thumbnail-scale: ${thumbnailScale};"
+                >
+                  <div style="
+                    width: ${plugins.shared.A4_WIDTH}px;
+                    height: ${plugins.shared.A4_HEIGHT}px;
+                    transform: scale(${thumbnailScale});
+                    transform-origin: top left;
+                    pointer-events: none;
+                  ">
+                    <dedocument-page
+                      .letterData=${this.letterData}
+                      .documentSettings=${this.documentSettings}
+                      .pageNumber=${i + 1}
+                      .pageTotalNumber=${this.thumbnailPages.length}
+                    ></dedocument-page>
+                  </div>
+                </div>
+                <span class="thumbnail__label">${i + 1}</span>
+              </div>
+            `
+          )}
+        </div>
+        <div
+          class="sidebar__resize-handle"
+          @mousedown=${this.startSidebarResize}
+        ></div>
+      </div>
+    `;
+  }
+
+  private getThumbnailScale(): number {
+    const previewWidth = this.sidebarWidth - 24; // Account for padding
+    return previewWidth / plugins.shared.A4_WIDTH;
+  }
+
   private renderZoomControls(): TemplateResult {
     return html`
       <div class="controls__section">
+        <!-- Sidebar Toggle Button -->
+        <button
+          class="controls__button sidebar-toggle ${this.showThumbnails ? "controls__button--active" : ""}"
+          @click=${() => this.toggleThumbnails()}
+          title="Toggle Thumbnails"
+        >
+          <dees-icon icon="lucide:panelLeft"></dees-icon>
+        </button>
+
+        <div class="controls__divider sidebar-toggle"></div>
+
         <!-- Zoom Out Button -->
         <button
           class="controls__button"
@@ -706,6 +938,44 @@ export class DeDocumentViewer extends DeesElement {
     this.pageGap = parseInt((e.target as HTMLInputElement).value, 10);
   }
 
+  // ============================================
+  // SIDEBAR METHODS
+  // ============================================
+
+  private startSidebarResize(e: MouseEvent): void {
+    e.preventDefault();
+    this.isResizingSidebar = true;
+
+    const startX = e.clientX;
+    const startWidth = this.sidebarWidth;
+
+    const onMouseMove = (moveEvent: MouseEvent) => {
+      const delta = moveEvent.clientX - startX;
+      const newWidth = Math.min(300, Math.max(100, startWidth + delta));
+      this.sidebarWidth = newWidth;
+    };
+
+    const onMouseUp = () => {
+      this.isResizingSidebar = false;
+      document.removeEventListener("mousemove", onMouseMove);
+      document.removeEventListener("mouseup", onMouseUp);
+      document.body.style.cursor = "";
+      document.body.style.userSelect = "";
+    };
+
+    document.addEventListener("mousemove", onMouseMove);
+    document.addEventListener("mouseup", onMouseUp);
+    document.body.style.cursor = "ew-resize";
+    document.body.style.userSelect = "none";
+  }
+
+  private updateThumbnailPages(): void {
+    const pageCount = this.getPageCount();
+    if (pageCount !== this.thumbnailPages.length) {
+      this.thumbnailPages = Array.from({ length: pageCount }, (_, i) => i);
+    }
+  }
+
   private handlePreviousPage(): void {
     const current = this.getCurrentPage();
     if (current > 1) {
@@ -861,11 +1131,16 @@ export class DeDocumentViewer extends DeesElement {
     super.updated(changedProperties);
 
     if (changedProperties.has("letterData")) {
-      // Update display zoom and page indicator after document renders
+      // Update display zoom, page indicator, and thumbnails after document renders
       setTimeout(() => {
         this.updateDisplayZoom();
         this.updatePageIndicator();
+        this.updateThumbnailPages();
       }, 100);
+      // Additional delay to ensure all pages are rendered
+      setTimeout(() => {
+        this.updateThumbnailPages();
+      }, 500);
     }
   }
 
@@ -896,16 +1171,21 @@ export class DeDocumentViewer extends DeesElement {
       resizeObserver.observe(viewport);
       this.registerGarbageFunction(() => resizeObserver.disconnect());
 
-      // Scroll listener for page indicator
+      // Scroll listener for page indicator and thumbnail highlighting
       const scrollHandler = () => {
         this.updatePageIndicator();
+        // Trigger re-render to update active thumbnail
+        this.requestUpdate();
       };
       viewport.addEventListener("scroll", scrollHandler);
       this.registerGarbageFunction(() => viewport.removeEventListener("scroll", scrollHandler));
     }
 
-    // Initial page indicator update
-    setTimeout(() => this.updatePageIndicator(), 300);
+    // Initial page indicator and thumbnail update
+    setTimeout(() => {
+      this.updatePageIndicator();
+      this.updateThumbnailPages();
+    }, 300);
   }
 
   // ============================================
@@ -1031,4 +1311,41 @@ export class DeDocumentViewer extends DeesElement {
   public async print(): Promise<void> {
     await this.handlePrint();
   }
+
+  /**
+   * Toggle the thumbnails sidebar visibility
+   */
+  public toggleThumbnails(): void {
+    this.showThumbnails = !this.showThumbnails;
+  }
+
+  /**
+   * Set whether the thumbnails sidebar is visible
+   * @param visible - Whether the sidebar should be visible
+   */
+  public setThumbnailsVisible(visible: boolean): void {
+    this.showThumbnails = visible;
+  }
+
+  /**
+   * Get whether the thumbnails sidebar is visible
+   */
+  public getThumbnailsVisible(): boolean {
+    return this.showThumbnails;
+  }
+
+  /**
+   * Set the sidebar width
+   * @param width - Width in pixels (100-300)
+   */
+  public setSidebarWidth(width: number): void {
+    this.sidebarWidth = Math.min(300, Math.max(100, width));
+  }
+
+  /**
+   * Get the current sidebar width
+   */
+  public getSidebarWidth(): number {
+    return this.sidebarWidth;
+  }
 }