On 8 May 2018, Mark Shuttleworth announced that the codename of Ubuntu 18.10, which was released on 18 October 2018, would be Cosmic Cuttlefish.
The Ubuntu 18.10 installation includes a new theme, named Yaru and the new icon theme, Suru.
Installation speeds are faster due to a lossless compression algorithm known as Zstandard. Startup speeds of pre-installed Snap applications were also improved.
In a review of 18.10 Joey Sneddon of OMG Ubuntu wrote, "Ubuntu 18.10 'Cosmic Cuttlefish' is a modest update compared to 18.04. The vast majority of notable improvements are tucked away out of sight, 'under the hood' ... Upstream GNOME Shell developers spent the past six months trying to lower GNOME Shell's memory usage and improve the overall performance of the shell, its animations, display manager, and parts of the GNOME extension framework (specifically Gjs), as we touched on in our recap of the new features in GNOME 3.30. Invisible and abstract though these changes are, they're appreciable. So much so that, if I had to describe this release in just one word it'd be 'peppy'. That's testament to the power of collaboration; with upstream devs and Canonical's engineering team working together."
Michael Larabel of Phoronix wrote, "Overall, Ubuntu 18.10 "Cosmic Cuttlefish" is quite a modest six-month upgrade for being the first past the Ubuntu 18.04 cycle. Exciting me the most, of course, is simply the package upgrades with riding Linux 4.18 + Mesa 18.2 for a much better Linux gaming experience and having moved on now to GCC8 ... What didn't get achieved for the Ubuntu 18.10 cycle is the long-awaited data viewer to the Ubuntu software/hardware survey introduced in 18.04 LTS ... As of writing there's still no public means of being able to view the statistics on these opt-in Ubuntu survey installations. Additionally, the plans for better Android phone integration with the Ubuntu 18.10 desktop by means of bundling GS Connect also didn't happen as planned for the Ubuntu 18.10 cycle."