What it does

• Library: your instances, with a pack-art header and an Overview of playtime, mods, worlds and recent screenshots. Play, update packs (with a preview that merges your config changes into the new version), manage mods, resource packs, shaders, worlds and screenshots, read logs and crashes.
• Performance: each run is recorded (FPS, 1% lows and frame times from Windows' present events, CPU, RAM, GPU, GC pauses and peak heap from Java's GC log, load time), and runs are compared side by side per Java argument preset. Nothing is injected into the game. FPS needs admin or the Performance Log Users group.
• Other launchers: manage Modrinth App, Prism / MultiMC, ATLauncher, GDLauncher and FTB App instances where they are, without copying them. CurseForge's folder is read in place too.
• Browse: CurseForge and Modrinth: install mods and modpacks, with dependencies.
• Servers: each server's loader, Java and mods, plus a diagnosis. With a server panel (Crafty Controller 4, MCSS, Pterodactyl / Pelican) you can start, stop, restart or kill it, see CPU, memory and players, use its console and its backups, through the panel's API. See Server panels for what each one supports.
• Hosting: run servers on your own PC: from a pack's official server pack or the instance's mods, with Java picked or downloaded for you, a server.properties editor, JVM presets, daily restarts with warnings and crash recovery. A backup mod's backups (SimpleBackups, FTB Backups, Advanced Backups…) are listed and restorable.
• Server sync: compare a server with its pack and push or pull mods and configs, with backups and undo.
• Logs & crashes: the game's live log, debug.log and crash reports, with search, an errors-only filter and mclo.gs sharing. Crash help names the mod behind a crash (certain, likely or possible), says what happened and offers the fix: install a missing mod, update the loader, put the last working version back or play without it. It can also install Crash Assistant, KostromDan's mod that explains crashes in game.
• Hopper Server: pair Hopper with Hopper Server, a server panel for Windows, Linux and Docker with a web UI: console, files, mods, players, backups (with off-site copies), schedules, alerts, people with roles, server addresses and sleeping servers. Server sync and server pack updates then work over the network.
• Accounts: several Microsoft accounts; try skins on an animated 3D model (walk, run, swim, dance and more), then change your skin (file, link or player name), cape and name.
• Ctrl+K: jump to any instance, tab, server or mod, or run an action.
• Ctrl+,: Settings, with a search over every setting (Ctrl+F there too).
• Peers: sync an instance with a friend's PC on your network.
• Themes: 19 themes, dark and light, plus your own theme files.

Screenshots

Install

Download hopper.exe from the latest release. Hopper runs on Windows 10 and 11 (64-bit).

Hopper Server has its own releases (tags hopperd-v…): a zip for Windows, tarballs for Linux x64 and ARM64, and the Docker image ghcr.io/watdafawx/hopperd (amd64 and arm64). See crates/hopperd/README.md for running it.

Run hopper.exe, then use Settings → Updates & install → Install. That copies Hopper into your apps with Start menu and desktop shortcuts, with no admin rights needed. Uninstall it from Windows Settings → Apps.

Update source in Settings → Updates & install takes a GitHub repository (owner/name). Hopper checks its latest release at start and updates itself from it.

Setup

• CurseForge: works out of the box with Hopper's built-in key. You can add your own key too: see CurseForge key.
• Folders: Settings → Library & folders points at your instances (CurseForge's Instances folder works) and Mojang's launcher; Settings → Servers at the folder your servers live in (see Your servers). Folders save as you leave the field, and the library refreshes.
• Other launchers: Settings → Other launchers lists the ones found on this PC; switch each on to see its instances in your Library. "Add a launcher folder…" covers a portable MultiMC or a moved instances folder.
• Server panel (optional): Settings → Servers takes the panel's address (e.g. https://myserver:8443) and an API key. For Crafty: your user → API Keys, with the Commands permission. Servers match by folder name, game port or name.
• Playing without the launcher (optional): needs MS_CLIENT_ID in .env, an Azure app id approved for the Minecraft API.

CurseForge key

CurseForge requires every app to use an API key for searching, installing and checking for updates (the files themselves come from CurseForge's download servers). Hopper's releases have Hopper's own key built in, so CurseForge works with nothing to set up.

You can still use a key of your own, which keeps CurseForge working even if Hopper's key is ever revoked:

1. Sign in at console.curseforge.com (free).
2. Open API keys and copy yours.
3. Paste it in Settings → CurseForge & Modrinth (or the setup wizard's "Use your own key instead"), and press Test.

Your key stays on your PC, in Windows Credential Manager, and only your copy of Hopper uses it. Once saved, it's used instead of the built-in one; Settings shows which key is in use. Modrinth needs no key at all.

Builds you make yourself have no built-in key: put CF_API_KEY=... in .env, paste your key in Settings, or build with .\scripts\release.ps1 -EmbedKey (see Build).

Files you download in your browser

Some mod authors only allow downloads from the CurseForge website, for every app. When a pack or a mod needs one of those, Hopper shows N files to download in your browser with Open pages. Download them as usual: Hopper watches your Downloads folder, checks each file against CurseForge's checksum, puts it in the instance (even when the browser renamed it to name (1).jar), and deletes it from Downloads.

Your servers

Hopper works with servers wherever their files can be reached as a folder:

• On this PC: use Host a server on this PC… on an instance (or + on the Servers page). Hopper downloads the pack's server files and runs them itself, with start/stop, console, scheduled restarts and backups. Nothing else to set up.
• On another PC in your home: share the folder that holds your server folders (right-click → Properties → Sharing), then on this PC either map it to a drive letter or use the \\PC-NAME\share path. Put that path in Settings → Servers → Server packs, and the PC's name in Server host (for status pings). Server sync then compares and copies files directly. If a panel such as Crafty, MCSS or Pterodactyl runs the servers, add it in Settings → Servers for start/stop, console and backups.
• At a host or on a VPS (no shared folder): Hopper can't copy files there yet. Get the server files with the instance's ⋯ → Download server pack… (when the pack publishes one), upload them with your host's file manager or SFTP, and if the host runs Pterodactyl, add it as the Server panel to control the server from Hopper.

Server panels

Hopper drives servers through their panel's own API, with an API key you make in the panel. The panel keeps running the servers; Hopper is the remote control. Set it up in Settings → Servers: add as many panels as you use, of any kind. Each server is found on the panel that runs it.

Server files over the network: Settings → Servers → Server files over SFTP or FTP. Point Hopper at a server's folder, or a folder of servers, on any SFTP, FTPS or FTP server: a rented host, Pterodactyl's SFTP, a PC with an SSH server. Hopper keeps a copy of each server's mods, configs and start scripts, fetches only files that changed, and uploads only what the sync changes. Files it replaces or removes on the server go to the server's own .hopper-backups/<time>/ first. The password (or key passphrase) is kept in Windows Credential Manager, and an SFTP server's key is remembered the first time: a different key later stops the connection.

Limits:

• Crafty: the API key needs the Commands permission (your user → API Keys). Tick "self-signed" for Crafty's own certificate.
• MCSS: doesn't report ports, so servers pair by folder or name. Key from Web Panel → API keys. Its API has no restore.
• Pterodactyl: needs a client key (ptlc_…, Account → API Credentials). For sync, add its SFTP under server files: port 2022, user <your panel user>.<server id>, your panel password (API keys don't work for SFTP). One entry per server for now.
• Server sync over SFTP or FTP: a server's loader can't be installed or updated over it (that runs on the server's PC); update the loader in the panel.
• Servers hosted by Hopper keep running when Hopper restarts (an update) or closes unexpectedly, and Hopper reconnects to them. Quitting stops them, saving the world first.

Build

Rust 1.98 (see rust-toolchain.toml).

cargo run --bin hopper                # debug build
.\scripts\release.ps1                 # dist\hopper.exe and a zip for a GitHub release
.\scripts\release.ps1 -EmbedKey       # same, with CF_API_KEY from .env built in
cargo test                            # library tests

Dev builds optimize dependencies, so GPUI runs at full speed. Only Hopper's own code stays unoptimized.

Layout

• src/*.rs is the library: CurseForge and Modrinth, instances, other launchers, installs, pack diffs, servers, hosting, server sync, peers, server panels, logs, accounts and self-update.
• src/gpui/ is the app.
• docs/ is the website (watdafawx.github.io/hopper), served by GitHub Pages from main. Screenshots live in docs/screenshots/; retake them with hopper --mcp (see below).

Hack on it

Hopper is plain Rust (no web stack), MIT licensed, and meant to be changed. Forks and pull requests are welcome: fix a bug, add a server panel or a launcher, or take it somewhere new.

• cargo run --bin hopper builds and runs it. Dependencies are optimized even in dev builds, so it runs at full speed while you work.
• A new server panel is one file implementing the ServerPanel trait (see src/panel/mcss.rs for a small one).
• Themes are JSON files: Settings → Appearance opens the folder, the refresh button loads them. No rebuild needed.
• hopper --mcp lets scripts and AI agents screenshot and drive the app, which helps when testing a change.
• Run cargo test --lib before sending a PR.

Scripting and testing

hopper --mcp serves MCP on http://127.0.0.1:47801/mcp. An agent can screenshot the window, read its state, navigate, click, hover, scroll and type, all without desktop control.

Dev arguments for scripted runs:

• --page browse|servers|sync|settings
• --instance <name> and --tab <tab>
• --search <text>
• --server <name>
• --theme "<name>", which applies for that run only
• --dialog new|export|versions|update|side

Releasing

Bump version in Cargo.toml, commit, then tag and push:

git tag v0.4.0
git push origin v0.4.0

The Release workflow builds hopper.exe and a zip and attaches them to the GitHub release; installed copies offer the update at their next start. The Release workflow builds Hopper's CurseForge key in (scrambled) from the CF_API_KEY repository secret; local builds only do with -EmbedKey.