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The launcher

The launcher installs Minecraft, keeps each setup in its own instance, signs you in, and starts the game. It has one main screen and one settings dialog with five tabs.

The main screen

Area What it does More
Notices strip The update banner and announcements from the Xol service. At most two rows tall until you open it. Accounts, versions and notices
Account button Shows the active player name. Opens the account menu. Accounts, versions and notices
Version switch and All versions Chooses the Minecraft version. Accounts, versions and notices
Profile list The profiles for the chosen version. Profiles
Performance preset Maximum FPS, Balanced, Quality or Battery Saver, with the trade-offs written out. Performance presets
Launch options Memory, window, Java and instance at a glance. The button opens settings. Launch options
Dock The state line, the progress bar and the Play, Cancel or Stop button. First launch

While a game is being prepared or is running, the version, profile and preset pickers are locked.

The settings dialog

Tab Contents More
Game Memory, window size, fullscreen Launch options
Java Custom Java executable, extra JVM arguments Launch options
Instance Instance picker, open-folder buttons, Repair, Clone, OptiFine import, the list of mods Xol did not install Instances, OptiFine
Service Xol access key, connection state, launcher updates and the Update automatically switch Updates
Support Export support log, the diagnostics switch, About Support log and crash reports

The left and right arrow keys move between tabs. Settings are saved as you change them; there is no Save button. A value the launcher cannot accept is refused with a message under the field, and the previous value stays.

How the launcher is built, briefly

The launcher's interface is a sandboxed page with no remote content. It cannot read files or start programs itself; it asks the main process, which validates every request. Links open only if their host is on a fixed list (Microsoft's sign-in and account pages, minecraft.net, xbox.com, optifine.net and Xol's own sites). Your Microsoft tokens and your access key live in the main process only and are never passed to the interface.