Gnome Shell vs Unity
Gnome Shell and Unity are desktop shells that take a similar approach to changing the presentation of menus and applications on the desktop.
 Relationship to Gnome 3
 Development criticisms
The Gnome 3 project, and Gnome Shell specifically, have been subject to delays. Despite this the project has had a large following.
Canonical and Gnome Project have been criticised as partisan for developing a new desktop shell, and including it as the default shell in Ubuntu 11.04 (previously it was the default only in Ubuntu Netbook Edition 10.10). The decision to make Unity the default was based on several items. firstly, gnome shell will not support touch capable devices. secondly Gnome shell will require 3d acceleration. 4
Unity is GPL 3 and LGPL 3, but also subject to Canonical's contributor agreement 5, requiring contributors to assign copyright to Canonical, and potentially allowing Canonical to release it under a different license.
The following features are common between both shells, even if they are based on different technologies.
 Application browser
Both remove the Gnome 2 menu in favour of an application browser, similar to the one found on MacOS, Windows 7, and smartphones. Both allow the user to pick application favourites. 6
 Desktop search
Both rely more heavily on desktop search, and provide a better desktop search experience. 6
 Display server
Both shells necessarily rely on a display server. Initially both use X. Gnome 3.8 provides experimental support for Wayland and Gnome 3.12 is planned to bring full support. Canonical has announced the development of their own display server called Mir. See also Wayland_vs_Xorg.
 File browser
Both use Gnome 3 Nautilus for file browsing.
Unity notifications are based on NotifyOSD.
 Window manager
Both shells necessarily rely on a window manager. Gnome Shell uses Mutter, Unity uses Compiz. See Compiz_vs_Mutter for details.
 Differential features
The following features occur only in one shell (by default), or have a significantly different interface.
 Look & feel
Each shell has a slightly different look and feel.
Shell's sidebar is accessible by:
- clicking on the "Activities" option on the top menu.
- forcing the mouse cursor in the upper left corner of the screen.
- pressing the Meta key on the keyboard (the Windows Key usually).
Unity's sidebar is always visible.
- Gnome Shell removes the minimise and maximise buttons by default (however, double-clicking on the title-bar will still let you maximize/restore), close button is on the right. You can change it using a tool named "gnome-tweak-tools".
- Unity has all three buttons on the left.
On Ubuntu 11.04 (Natty Narwhal), Unity is installed by default, Gnome 2 is available as a fallback. Gnome Shell was not included because it was not complete in time for the 11.04 release, but it may be possible to install Gnome Shell from a PPA. 7 8 9
On Ubuntu 11.10 (Oneiric Ocelot), Unity will be installed by default and a 2D non-Compiz version of Unity will be available as a fallback for lower-end machines. 8 10 It will not include Gnome Shell, but Gnome Shell will be available from the Ubuntu repositories.
Linux Mint 10 and 11 will use neither Gnome Shell nor Unity, rather keeping the Gnome 2 desktop shell. 11 The user will have to install a package if they want either interface.
Fedora 15 and 16 both come with Gnome Shell installed by default. Unity will not be available for Fedora.
 Further reading
- Why is Ubuntu 11.04 switching to Unity?
- How hard would it be to merge Unity & Gnome Shell? (includes notes on underlying languages)
- Question (not debate): What's the difference between Unity and Gnome Shell 3