Sidebery: Vertical Tab Sidebar for Firefox with Tree Structure and Session Snapshots

If you work with many tabs, Firefox's default tab bar is a horizontal row that eventually becomes unusable. Sidebery moves your tabs to a vertical sidebar with tree structure, groups, and session management — transforming how you organize browser sessions.

Why a Vertical Tab Sidebar

The problem with horizontal tabs:

• At 15+ tabs, tabs shrink to icons with no visible titles
• You can't see what's open at a glance
• Navigation requires clicking through tabs or using Ctrl+Tab cycling
• No visual grouping of related tabs

Sidebery puts tabs in a vertical panel. Benefits:

• Tab titles are always readable (you have all vertical screen space)
• Tree structure: child tabs indent under parent (open a link from a tab = its child)
• Collapsible groups for organizing related tabs
• Pinned tabs stay pinned but separate
• Search box to find any open tab

Installing Sidebery

addons.mozilla.org → search "Sidebery" → Add to Firefox.

After installing:

1. A sidebar icon appears in your toolbar
2. Click it to open the Sidebery sidebar
3. By default, it appears on the left side
4. Optionally: hide the original horizontal tab bar (via Sidebery settings + userChrome.css)

Hiding the Horizontal Tab Bar

To get a clean UI with only the Sidebery sidebar:

1. Create a userChrome.css file:

Find your profile folder: about:support → Profile Folder → Open Folder

Create chrome/userChrome.css:

/* Hide horizontal tab bar */
#TabsToolbar {
  visibility: collapse !important;
}

/* Optionally: make the sidebar wider */
#sidebar-box {
  min-width: 200px;
  max-width: 400px;
}

1. Enable userChrome.css:
   • about:config → toolkit.legacyUserProfileCustomizations.stylesheets = true
   • Restart Firefox

Now Firefox shows the Sidebery sidebar without the horizontal tab bar. Clean, vertical-only tab management.

Tree Structure: How It Works

When you Ctrl+click a link (or right-click → Open in New Tab from a context menu), the new tab is a child of the current tab.

In Sidebery:

• Parent tab shows with an arrow/indent indicator
• Child tabs appear below, indented
• Collapsing the parent hides all children
• Closing the parent can optionally close all children (configurable)

Practical example:

1. Search Google
2. Open 5 results in new tabs
3. Those 5 tabs are children of the Google search tab
4. Collapse the Google tab → all 5 results hidden
5. Expand when you want to compare them

This is much more useful than the flat tab list.

Tab Groups

Sidebery supports explicit tab groups (independent of the tree):

1. Right-click in the Sidebery sidebar → Create Group
2. Drag tabs into the group
3. Collapse/expand the group
4. Name the group

Groups are good for manually organizing tabs that don't have a natural parent-child relationship.

Searching Open Tabs

In the Sidebery panel, there's a search icon (or press Ctrl+Space by default in some Sidebery versions). Type to filter tabs by title or URL.

This replaces the awkward Ctrl+Tab cycling for finding a specific tab by name.

Session Management with Sidebery

Sidebery can save and restore sessions of tabs:

Snapshots: Sidebery automatically takes snapshots of your tabs periodically. Access via: Sidebery icon → Menu (gear icon) → Snapshots

Creating a named snapshot:

1. Sidebery menu → Create Snapshot
2. Give it a name
3. Saved snapshots can be restored later

This is similar to a session manager extension, but integrated with the tab tree structure. A restored snapshot brings back the full tree, not just a flat list of URLs.

Combination with Tab Manager & Session Saver extension: For cross-device session sync, use Firefox Sync for "open tabs" and a dedicated session manager. Sidebery's snapshots are local-only; they don't sync across devices. If you want sessions accessible on multiple machines, export from Sidebery and use a separate sync method.

Sidebery Settings Worth Knowing

Access via: Sidebery icon → gear icon → Settings

Tab behavior:

• "Create child tab on middle-click": links opened by middle-click become tree children
• "Activate parent after close": when closing a child, activates parent
• "Move child tabs to parent if parent closed": reorganizes tree on tab close

UI:

• Colorize tabs by container (if using Multi-Account Containers)
• Show close button: always / on hover
• Tab height: compact / normal / wide

Sidebar position: Settings → Sidebar → Position (left or right)

Using Sidebery with Multi-Account Containers

If you use Firefox Multi-Account Containers, Sidebery colors the tabs by container. Each container gets a border color, making it visually obvious which tabs belong to which context (Work, Personal, Shopping, etc.).

This is genuinely useful visual differentiation — you can see at a glance which tab is in which container without reading the label.

Keyboard Shortcuts in Sidebery

Sidebery adds some new keyboard actions:

• Ctrl+.: Focus the Sidebery sidebar (navigate with arrow keys)
• Ctrl+Shift+C: Create a new container tab

Configure more in Sidebery settings → Keybindings.

Sidebery vs Tree Style Tab

The other major vertical tab extension for Firefox:

Feature	Sidebery	Tree Style Tab
Active development	Yes	Yes
Container coloring	Yes	Yes
Session snapshots	Yes	Limited
Groups	Yes	Limited
Customization	Very deep	Deep
Performance	Good	Good
Complexity	More	Less

Tree Style Tab is the long-established option; Sidebery is the newer, more feature-rich option. Both are good. Sidebery has more built-in features; Tree Style Tab is simpler.

Performance Note

With 200+ tabs, Sidebery's rendering can slow down slightly (it's rendering a large virtual list). For extreme tab counts (500+), consider whether session management is a better solution than keeping all tabs open simultaneously.

The Tab Manager & Session Saver extension pairs well with Sidebery: save current sessions to disk, close the tabs, and use Sidebery's tree for the tabs you're actively working on.