Nightcap is Roblox on Linux, tuned for desktop play. It is a Mocktail fork
that keeps up with Roblox updates, with extra bug fixes, custom assets and
more. It runs the Android `x86_64` Roblox client on Linux, including a Linux
userspace hosted by FreeBSD's Linuxulator. It provides the Android ABI and JNI
pieces the client expects, then connects them to SDL3 and Vulkan or OpenGL on
the Linux side.
Nightcap is an independent community project. It is not affiliated with Roblox
Corporation or VinegarHQ and does not distribute the Roblox client.
## About this fork
Nightcap is a fork of [komaruworld/mocktail](https://github.com/komaruworld/mocktail)
with extra fixes for playing on a PC. The program and config paths keep the
`mocktail` name so upstream fixes still apply cleanly. The app ID is
`io.github.CoderDayton.nightcap`, so Nightcap and upstream can be installed
side by side.
- **Keeps up with Roblox.** New Roblox versions work soon after they come out.
- **Plays more games.** Nightcap answers a server check that some experiences
use, so you can join and stay in those too.
- **Voice chat that keeps working.** Your microphone still works after a
Roblox update.
- **Logging in works.** Verification checks and captchas finish instead of
hanging.
- **The current Roblox look.** The new home screen and side menu, like on
Windows.
- **Your own cursors, fonts and skies.** Drop files in
`~/.local/share/mocktail/asset_overlay` and Nightcap uses them. The layout
matches Sober's `asset_overlay` folder.
- **Smoother mouse and a cooler PC.** Optional raw mouse input, and less CPU
use while idle.
Everything else works the same as upstream. See
[`textures/`](textures/README.md) for custom textures, a ready-made crosshair
and the asset overlay folder, the [roadmap](docs/ROADMAP.md) for what is
coming next, the [changelog](CHANGELOG.md) for what each release changed,
[performance](docs/PERFORMANCE.md) for CPU load, heat and the knobs that change
them, and the [FAQ](FAQ.md) for Discord RPC, logs, and VR.
## Install with Flatpak
```bash
flatpak install --user https://coderdayton.github.io/nightcap/nightcap.flatpakref
flatpak run io.github.CoderDayton.nightcap
```
Updates arrive through `flatpak update`. Nightcap is not on Flathub yet.
## AppImage
Grab the AppImage from the
[latest release](https://github.com/CoderDayton/nightcap/releases/latest),
make it executable, and run it:
```bash
chmod +x Nightcap-x86_64.AppImage
./Nightcap-x86_64.AppImage
```
## Distribution packages
Each release also carries a DEB, an RPM, and a pacman package, with a
`.sha256` beside every file on the
[releases page](https://github.com/CoderDayton/nightcap/releases/latest):
```bash
sudo apt install ./nightcap__amd64.deb
sudo dnf install ./nightcap--1.x86_64.rpm
sudo pacman -U nightcap--1-x86_64.pkg.tar.zst
```
They install `/usr/bin/mocktail`, so they conflict with upstream's `mocktail`
package.
On Arch Linux, [`nightcap-git`](https://aur.archlinux.org/packages/nightcap-git)
is on the AUR. It builds the current `main` branch and is maintained by
[@dim-ghub](https://github.com/dim-ghub):
```bash
yay -S nightcap-git
```
Nightcap is in no other distribution repository.
Or build and install from source using the steps under
[Building](#building).
## How it works
```
Roblox APK -> signature and ABI checks -> Bionic + JNI -> SDL3 + Vulkan/OpenGL
```
The APK is checked before any native code is loaded. It is downloaded on first
launch and is not bundled with Nightcap. The last working copy is kept in case
an update fails.
A leftover `.previous_good-recovery.json` in the payload store marks pending
recovery after a publication or restoration failure and blocks further payload
publication and garbage collection. Check `current.json` and `previous_good.json`
against the saved recovery state and fix the underlying problem before manually
removing the marker.
Screenshots
## FFlag overrides
Put a JSON object in `$XDG_CONFIG_HOME/mocktail/fflags.json` (usually
`~/.config/mocktail/fflags.json`). Nightcap applies it on the next launch.
PC profiles use the legacy Charts page by default to avoid the blank screen
caused by `Color3` errors in the newer SDUI page. An explicit
`FFlagLuaAppChartsAppPage` override takes precedence over this default.
PC profiles also set `FIntFlyoutTestVariantRollout12` to `2`, which shows the
desktop side panel menu. An explicit override takes precedence.
```json
{
"FFlagExample": "True",
"DFIntExample": "120"
}
```
## Settings
Edit `~/.config/mocktail/config.yaml`. Useful options:
- `graphics.frame_rate_limit: display` to unlock FPS to your monitor's rate.
- `graphics.vsync: off` for the lowest lag, at the cost of tearing.
- `graphics.backend: opengl` if Vulkan does not work on your GPU.
## Building
Linux `x86_64` is supported. Experimental FreeBSD 15.1 Linuxulator support has
been tested with an `x86_64` Fedora 44 userspace. On FreeBSD, Nightcap runs
inside Linuxulator; it is not a native FreeBSD binary. Building requires CMake
3.20+, Git, pkg-config, LLD, binutils, a C++17 compiler, SDL 3.4+, SDL3_ttf,
Vulkan, EGL, libplacebo, fontconfig, libcurl, OpenSSL, libelf, libyaml, libpng,
minizip, Capstone 5, utf8proc, nlohmann/json, GTK4, libadwaita 1.6+, and
WebKitGTK 6.0.
See the [FreeBSD Guide](packaging/freebsd/README.md) for setup and launch instructions.
Ubuntu 26.04+
```bash
sudo apt update
sudo apt install build-essential cmake git ninja-build pkg-config lld \
libsdl3-dev libsdl3-ttf-dev libcurl4-openssl-dev libssl-dev \
nlohmann-json3-dev libyaml-dev libpng-dev libelf-dev libminizip-dev \
libcapstone-dev libgtk-4-dev libadwaita-1-dev libwebkitgtk-6.0-dev \
libutf8proc-dev libfontconfig1-dev libegl-dev libvulkan-dev \
libplacebo-dev zlib1g-dev
```
Arch Linux
```bash
sudo pacman -S --needed base-devel cmake git ninja pkgconf lld sdl3 sdl3_ttf \
curl openssl nlohmann-json libyaml libpng libelf minizip capstone gtk4 \
libadwaita webkitgtk-6.0 libutf8proc fontconfig libglvnd \
libplacebo vulkan-headers vulkan-icd-loader zlib
```
Fedora 44+
```bash
sudo dnf install gcc-c++ cmake git ninja-build pkgconf-pkg-config lld \
SDL3-devel SDL3_ttf-devel libcurl-devel openssl-devel \
nlohmann-json-devel libyaml-devel libpng-devel elfutils-libelf-devel \
minizip-ng-compat-devel \
capstone-devel gtk4-devel libadwaita-devel webkitgtk6.0-devel \
utf8proc-devel fontconfig-devel libglvnd-devel vulkan-headers \
vulkan-loader-devel libplacebo-devel zlib-ng-compat-devel
```
```bash
git clone --recurse-submodules https://github.com/CoderDayton/nightcap.git
cd nightcap
make build
./build/mocktail
```
To install it for your user, with an app menu entry and Roblox link handling:
```bash
make install PREFIX=~/.local
```
Use `sudo make install` instead to install system-wide under `/usr`. To make
Roblox website links open the build tree copy without installing, run
`make register-url-handler`.
To build and install the Flatpak from source, install `flatpak-builder` and run
`make flatpak`. It builds with 2 parallel jobs to keep memory use low. Pass
`FLATPAK_JOBS=N` to `make flatpak`, or set `MOCKTAIL_FLATPAK_JOBS=N` for
`scripts/build_flatpak.sh`, to change that.
To run the same checks as CI before each commit and push, install
[lefthook](https://github.com/evilmartians/lefthook) and run once:
```bash
lefthook install
```
## Known limitations
Nightcap does not currently work with `hardened_malloc`. Using
`hardened_malloc` may cause Nightcap to fail to start or crash during runtime.
Run Nightcap without `hardened_malloc` enabled.
## License
[Apache License 2.0](LICENSE). Third-party components keep their own licenses.
## Support
Support this fork by giving it a star or with cryptocurrency:
- LTC: `LdABR2ELRYrUESWZWrEk1uNx38gHHMuHUU`
- SOL: `tjeDnPoWeyW8zfTf8c5CVAm5QTV8vFPaPouaScAdwfT`
Support the upstream project, which does most of the heavy lifting:
- USDT (TON): `UQCi6Yzcc9cOctoij6n_r1K90-OdVxAT0D_xo2UzGKkQaJDY`
- USDT (TRC20): `TNPMG9Vig2xiuo2r1QqnXRChPH7Vu28Jmx`
