Horizon offline launcher.
One switch in Settings.
The xHorizon launcher can download the official Mojang 26.3 jars and prepare Horizon without a Microsoft session. It then starts the game offline under a nickname you choose.
Official Horizon client: github.com/horizon-rust/horizon/releases. The xHorizon launcher downloads it for you.
From installed game to offline launch
Download official 26.3
Open Diagnostics and press Download 26.3 & prepare. The launcher fetches the official Mojang jars, checks SHA-1 and prepares the game files itself.
Switch offline on
Settings, Offline, then Play offline. Choose a nickname of 3 to 16 letters, digits or underscores. The launcher saves it and stops passing a session file.
Play the same profile
Press Play on Home or on a pack. Worlds, options, shaders and screenshots stay in the profile folder; only the account step is gone.
What the switch changes
The launch
The client starts with --name and without --session-file. That is the whole mechanism. No token is written, renewed or stored by the offline path.
Server login
Servers that verify a licensed account reject the nickname. Singleplayer, LAN worlds and servers running in offline mode accept it.
Skins and capes
No account skin or cape is sent. Other players see the default look until you switch back and sign in.
Packs and native mods
A pack with its own native build starts that build. A pack that was never installed or built still needs its normal install first.
Questions this page gets
Is offline mode a separate launcher build?
No. It is a setting in the same launcher, in the Offline section. The Play button changes how it starts the game, not which app you open.
Do I still need the official Horizon launcher?
For the first setup, yes. The official launcher signs in, prepares the game from your Minecraft copy and installs versions. The xHorizon shell reuses that installation.
Does offline mode work with a modpack?
Yes. The selected pack starts with its own mods and native build. If the pack was never installed, install it once with a session, then switch offline mode on.
How do I go back online?
Open Settings, Offline, and switch it off. The next Play uses the signed-in account again. Worlds created offline stay in the same profile.
Does it update the game?
No. Game and launcher updates still come from their normal channels. Offline mode only changes the launch step.
Install once. Launch either way.
The offline switch is part of the same launcher. Download the preview, prepare the game once, and choose the account mode on each launch.
Offline mode starts prepared game files without a Microsoft session. It is not a license bypass and does not include Minecraft. Terms.