Multi Roblox Manager

A Windows desktop app to run multiple Roblox accounts side-by-side in separate Roblox processes. Built with .NET 8 + WPF.

Features

• Multi-instance: holds the ROBLOX_singletonEvent named mutex so additional Roblox processes can launch.
• Per-account auth: stores .ROBLOSECURITY cookies and fetches a fresh authentication ticket for each launch (no cookie injection into a running client).
• Encrypted storage: account data is encrypted on disk with Windows DPAPI (CurrentUser scope — only your Windows account can decrypt it).
• Batch launch: select N accounts, paste a game URL or place ID, click Launch — staggered with a configurable delay.
• Camera-grid Instances view: live DWM thumbnails of every running Roblox window. Double-click any tile to enter Play mode — the Roblox window is repositioned over the app's play area and given focus so you can play inside it. "Back to Grid" sends it back.
• Account avatars: headshot thumbnails pulled from the Roblox thumbnails API.
• Window management: arrange all Roblox windows in a desktop grid, minimize all, or focus a single instance.
• Tabbed UI: Accounts and Instances tabs in a dark, card-based layout.

Quick start

Requirements:

• Windows 10/11
• .NET 8 SDK (build) or .NET 8 Desktop Runtime (run)
• Roblox installed

Clone and run:

git clone https://github.com/<you>/roblox-multi-instance.git
cd roblox-multi-instance
dotnet run --project src/RobloxMultiInstance

Or build a release binary:

dotnet publish src/RobloxMultiInstance -c Release -r win-x64 --self-contained false -o publish
.\publish\RobloxMultiInstance.exe

Using it

1. Accounts tab → Add an account: click + Add Account, paste a .ROBLOSECURITY cookie, click Validate to confirm, then Save. Avatar headshot is fetched automatically.
2. Enter a game: paste a Roblox game URL (e.g. https://www.roblox.com/games/920587237/...) or the place ID directly.
3. Select accounts: check the boxes for the accounts you want to launch.
4. Launch: click Launch Selected. Each account opens in its own Roblox process.
5. Switch to the Instances tab to see live thumbnails of every Roblox window in a camera-grid layout.
6. Click "Play Here" on any tile (or double-click) to enter Play mode: that Roblox window is moved over the play area and brought to the foreground so you can move/control it directly. Other instances stay in a side panel of mini-thumbnails — click "Switch" on any of them to hand control over. Click "Back to Grid" to return.

Getting your .ROBLOSECURITY cookie

1. Log into roblox.com in a browser.
2. F12 → Application tab → Cookies → https://www.roblox.com.
3. Copy the value of the .ROBLOSECURITY cookie (it starts with _|WARNING:-DO-NOT-SHARE-THIS...).

Treat this cookie like a password — anyone who has it can sign into your account.

How it works

The mutex trick

Roblox prevents itself from launching multiple times by checking a named mutex called ROBLOX_singletonEvent. On startup, this app opens a handle to that mutex and keeps it for the app's lifetime. With the mutex already in existence, the Roblox client's singleton check stops blocking additional launches.

The auth ticket dance

.ROBLOSECURITY cookies are session tokens that the Roblox website uses. The Roblox player binary doesn't accept the cookie directly — it expects a short-lived authentication ticket. Each launch does:

1. POST https://auth.roblox.com/v1/authentication-ticket/ with the cookie → server returns a 403 with an x-csrf-token header.
2. POST the same URL again with X-CSRF-TOKEN + RBXAuthenticationNegotiation: 1 headers → server returns rbx-authentication-ticket.
3. Construct a roblox-player: URI with gameinfo:<ticket> + placelauncherurl:<encoded launcher URL> and start it with Process.Start.

Storage

Accounts live in %LOCALAPPDATA%\RobloxMultiInstance\accounts.dat, encrypted with DPAPI (CurrentUser scope). The file is unreadable on another machine or under another Windows user.

Live thumbnails

The Instances view uses DWM thumbnails — the same API Windows uses for Alt+Tab previews. DwmRegisterThumbnail registers each Roblox window's HWND as a thumbnail source for our app, and DwmUpdateThumbnailProperties repositions the destination rectangle on every layout pass. DWM composites the live window contents into our app at near-zero cost.

Process-to-account association is done by snapshotting the set of RobloxPlayerBeta.exe PIDs immediately before launch, then claiming the next-appearing new PID for that account.

Click-to-control

Play mode moves the selected Roblox window over the app's play area via SetWindowPos. When you click "Back to Grid", the window is restored to its prior position. This avoids the complexity (and crashes) of true SetParent window reparenting while still giving an embedded feel.

Security notes

• Cookie storage is encrypted at rest, but the cookie is loaded into memory while the app runs. Don't run this on shared / untrusted machines.
• The app does not exfiltrate cookies — it only talks to auth.roblox.com and users.roblox.com. Audit src/RobloxMultiInstance/Services/RobloxAuth.cs to confirm.
• This is a third-party tool, not affiliated with or endorsed by Roblox Corporation.

Project layout

src/RobloxMultiInstance/
  App.xaml / App.xaml.cs              # entry, DI-lite singletons, dark theme
  MainWindow.xaml / .cs               # shell: top bar with nav tabs + mutex indicator
  Views/
    AccountsView.xaml / .cs           # account list, batch launch
    InstancesView.xaml / .cs          # camera-grid + play mode
    AddAccountWindow.xaml / .cs       # add/edit account dialog
  Models/
    Account.cs                        # alias, cookie, username, avatar URL
    RobloxInstance.cs                 # PID, HWND, account binding
  Services/
    MutexHolder.cs                    # ROBLOX_singletonEvent
    AccountStore.cs                   # DPAPI-encrypted JSON store
    RobloxAuth.cs                     # CSRF + auth ticket flow + avatar API
    RobloxLauncher.cs                 # roblox-player: URI construction
    RobloxProcessTracker.cs           # polls processes, associates with accounts
    WindowManager.cs                  # focus / move / arrange wrappers
    Win32.cs / Dwm.cs                 # P/Invoke
  Controls/
    DwmThumbnailHost.cs               # WPF FrameworkElement hosting a DWM thumbnail
  ViewModels/
    MainWindowViewModel.cs            # tab nav + mutex pill
    AccountsViewModel.cs              # account-side commands
    AccountItemViewModel.cs           # per-account row
    InstancesViewModel.cs             # live tracker → tiles
    InstanceTileViewModel.cs          # per-instance tile
    AddAccountViewModel.cs            # add/edit dialog
  Converters/Converters.cs

License

MIT — see LICENSE.