User Guide

Kepler is currently in private testing and downloads are not yet available. When released, it runs on Windows, macOS, and Linux; the required Java runtime is selected automatically from Mojang's version manifest and downloaded from official sources, so no manual Java installation is needed.

• Why the SmartScreen prompt appears: Kepler is a new application and is not yet signed with a digital code-signing certificate. Windows Defender SmartScreen may display the blue Windows protected your PC screen for new binaries; this is not a malware detection, only an unrecognized publisher notice.
• Step-by-step installation: Click the More info link beneath the message on the SmartScreen dialog, then click the Run anyway button in the bottom-right corner to proceed.
• SHA-256 verification: To verify file integrity, run Get-FileHash .\KeplerClient-Kurulum.exe -Algorithm SHA256 in Windows PowerShell and compare the output hash with the official SHA-256 checksum listed on the download page.

On first launch, the setup wizard walks you through initial preferences. You can re-run the wizard anytime from Settings > Advanced > Re-run setup or navigate quickly using the Ctrl+K command palette.

• Adding an account: Open the account menu in the top-right corner to sign in with an official Microsoft/Xbox account via PKCE OAuth2 in your system browser (refresh tokens are stored in your OS keyring), or create a local 3–16 character Offline account for singleplayer use.
• Ready or custom profile: Start with the out-of-the-box optimized profile or create a clean or modded (Fabric, Quilt) instance from Library > + New profile. Minecraft 1.21.x with Fabric is supported first; 6 versions from 1.20 to 26.3 are in testing.
• Importing from other launchers: Automatically scan installed launchers (such as Prism Launcher or Modrinth App) and import existing profiles along with their worlds.

Kepler's mod catalog starts with Modrinth. Kepler does not distribute pre-packaged modded game archives; all mods are downloaded directly from official sources with SHA-1 verification.

• Searching and installing mods: Select your target profile on the Discover screen and search the Modrinth catalog. Mod compatibility and required dependencies are resolved automatically for your profile's game version.
• Managing and updating mods: In a profile's Mods tab under Library, filter installed mods by All, Enabled, or Disabled, and click Check for updates to inspect new releases.
• .mrpack modpacks: Import Modrinth .mrpack and compatible .zip archives with path traversal protection and allowed-domain filtering, or export your profile as a package.

Share your profile setup without sending large archive files by using a compact KEPLER1: profile share code.

• Payload structure: Prefixed with KEPLER1: followed by URL-safe Base64 JSON, the code encodes schema version, profile name, Minecraft version, optional mod loader info, and Modrinth mod identifiers (project_id, version_id, filename).
• Privacy and validation limits: A share code never includes file contents, local filesystem paths, account credentials, or private settings. Imports validate a maximum size of 64 KB and up to 500 mods.
• Settings export: You can also export and import launcher configuration, themes, and server lists as a standalone JSON file.

For computers with limited memory or modest processors, Kepler provides hardware analysis and tuned launch presets.

• Low-hardware preset: In profile settings under Performance preset, choose between Low hardware (low-spec PC mode), Balanced, or High performance JVM flag templates.
• Automatic RAM and calibration: Recommended heap allocation is calculated from your total/available system RAM, CPU core count, mod count, and Minecraft version. The in-launcher 2‑3 minute calibration tests 3–4 candidate profiles and selects the winning profile for your hardware.
• Lightweight UI toggles: Disable launcher animations and enable Compact view under Settings > Game.

In-game screenshots for each profile are stored separately inside that instance's <profile>/screenshots directory.

• Browsing and previewing: The launcher lists .png screenshots for the selected profile sorted newest first (up to 500 screenshots per query and 12 MB per image).
• Deleting and opening folder: Delete unwanted screenshots directly from the launcher or open the profile's screenshots directory in your operating system's default file manager.

Before adding mods or changing versions, safeguard your data from the Backups tab inside any profile in Library.

• Atomic .zip backups: Click Create backup, select either Worlds only or Full profile scope, add an optional label, and generate a one-click .zip archive.
• Safe restore: View existing backups with date and size metadata, delete old archives, or run Restore backup—which automatically creates a safety backup before restoring.

Connect directly to multiplayer servers either from the in-launcher Servers screen or via command-line launch flags.

• Server list and SLP ping: Save multiplayer servers, monitor online status, player count, and latency (ms) individually or in bulk using the Server List Ping (SLP) protocol, and click Join to launch directly into a server.
• CLI launch flags: Start Kepler with --server <host[:port]>, --port <n>, and --profile <id> (or --server=host:port) to connect your chosen profile straight to the target server.
• Address validation: Malformed addresses containing spaces and link-local/metadata (169.254.x.x) addresses are rejected for security.

When the game exits unexpectedly, the process supervisor inspects the exit code and the ring buffer of recent stdout/stderr console lines.

• Conflict detection: Under Performance > Troubleshooter, Kepler lists likely crash causes and suspected conflicting mods; you can disable a conflicting mod with one click via Disable mod or Try fix.
• Privacy masking: When using Copy report or Share log, a privacy filter automatically masks your username and local system file paths.

Common warnings and how to resolve them:

• "Game is already running" (already_running): An active Minecraft process is running in the background. Click Stop on the home screen or wait for the process to exit before launching again.
• Game crashes on startup: Two mods may have a rendering or API conflict. Open Performance > Troubleshooter and disable the suspected mod.
• Out of memory or stuttering: Too little RAM or more than 75% of system memory may be allocated to the profile. Enable Automatic RAM in profile settings or re-run the calibration test.
• Unsupported Java (unsupported_java): Open Performance > Java and use Auto-detect/download Java for the selected Minecraft version.
• Microsoft sign-in does not complete: If browser authentication timed out, click Cancel and start the sign-in flow again.