Captail is a lightweight, open-source alternative to NVIDIA ShadowPlay Instant Replay. It continuously keeps the latest seconds or minutes in a rolling buffer and saves them when you press a hotkey.

Captail is designed around one rule: Instant Replay should stay on. A game crash, game-to-desktop switch, temporary capture failure, protected surface, or recoverable graphics-driver interruption should not silently leave you without a replay. A watchdog monitors the recording pipeline and restarts it when recovery is possible.

Warning

Captail v0.1.x is an early public preview. Core recording works, but bugs and hardware-specific problems are expected. Please report anything that does not work.

Why Captail?

• Small, focused UI — replay state, active source, audio, hotkey, and disk space at a glance.
• Resilient rolling buffer — health monitoring and automatic pipeline recovery.
• DRM-tolerant behavior — protected sections may appear black, but the buffer is designed to continue instead of disabling itself.
• Real high-frame-rate capture — 30, 60, 120, 144, or 240 FPS without generated duplicate frames.
• Game or desktop capture — per-game Game Capture or Windows desktop capture.
• Hardware encoding — AV1, HEVC, and H.264 through supported NVIDIA NVENC, AMD AMF, or Intel Quick Sync encoders.
• Flexible audio — system/game audio and microphone, volume controls, microphone boost, mixed or separate tracks.
• Local and private — no account, cloud upload, analytics, or telemetry. Replays stay on your PC.

How Captail differs from OBS Replay Buffer

Captail uses libobs for capture and encoding, but it is not an OBS Studio frontend.

• Starts directly in the system tray with Windows.
• Requires no scenes, sources, or streaming configuration.
• Monitors capture health and automatically recovers the recording pipeline.
• Switches between focused game capture and desktop capture.
• Stays focused on one job: reliable instant replay.

Download

Download the latest version from GitHub Releases.

Package	Best for	What to do
Captail-x.y.z-Setup-win-x64.exe	Most users	Run installer. Captail and all required runtimes are installed automatically. An uninstaller is added to Windows Settings.
Captail-x.y.z-Portable-win-x64.zip	Portable use	Extract the complete folder, then run Captail.exe.
SHA256SUMS.txt	Verification	Compare downloaded file SHA-256 before running it.

Both packages are self-contained. OBS Studio and .NET do not need to be installed separately.

Note

Current binaries are not Authenticode-signed. Windows SmartScreen may show an “Unknown publisher” warning. Verify the SHA-256 checksum and GitHub build provenance before running a release.

Quick start

1. Install Captail or extract the Portable ZIP.
2. Launch Captail.exe.
3. Select Desktop or a running game under Source.
4. Choose buffer length, codec, resolution, FPS, and audio sources.
5. Keep Instant Replay enabled.
6. Press Ctrl+Shift+F10 to save the current buffer.

Default hotkeys:

Action	Hotkey
Save replay	Ctrl+Shift+F10
Enable or disable Instant Replay	Ctrl+Shift+F9

Both hotkeys can be changed in Settings.

Features

Capture and video

• Selected-process Game Capture with anti-cheat compatibility mode.
• Windows Graphics Capture for desktop recording.
• AV1, HEVC/H.265, and H.264/AVC when supported by GPU and driver.
• Automatic GPU and encoder capability detection.
• GPU-aware encoder profiles for NVIDIA, AMD, and Intel hardware.
• Adaptive automatic bitrate or manual bitrate.
• Source resolution, 720p, 1080p, 1440p, or 4K.
• 30, 60, 120, 144, and 240 FPS.
• Duration limit and optional maximum replay-buffer size.

Audio

• System audio or selected-game audio.
• Microphone capture.
• Separate system/game and microphone volume controls.
• Microphone boost up to +20 dB.
• One mixed track or separate audio tracks.
• AAC in fragmented MP4 or Opus in MKV.

Windows integration

• Configurable global hotkeys.
• System tray with double-click restore.
• Start with Windows.
• Native overlay notifications for replay state and saved clips.
• Single-instance protection.
• English interface by default, with live English/Russian switching.

Reliability

• Recording-pipeline watchdog.
• Automatic replay restart after recoverable capture or encoder failure.
• Progressive retry delay when the graphics driver is temporarily unavailable.
• Fragmented MP4 output to reduce the risk of losing an entire file after interruption.
• Protected/DRM surfaces may become black while the rolling buffer continues.

Hardware compatibility

Hardware	Status
NVIDIA GeForce RTX 50 series	Tested
NVIDIA GeForce RTX 40 series	Tested
Older NVIDIA GPUs	Not yet verified; expected to work when supported by libobs/NVENC
AMD GPUs	Capability detection implemented; public hardware testing needed
Intel GPUs	Capability detection implemented; public hardware testing needed

Captail currently targets Windows 10 version 2004 or newer and Windows 11, x64.

Codec availability depends on GPU generation and installed graphics driver. Captail hides unavailable codecs automatically.

Known limitations

• This is the first public version. Expect bugs.
• Captail is currently unsigned, so SmartScreen may warn on first launch.
• Unique 240 FPS frames require the game and capture path to produce 240 distinct frames. Desktop capture is limited by desktop/monitor presentation rate.
• Some games or anti-cheat configurations may block Game Capture.
• DRM-protected video cannot be captured; protected regions may be black.
• NVIDIA generations older than RTX 40, AMD, and Intel need broader real-world testing.

Reporting bugs

Feedback is especially valuable during this preview.

1. Check existing issues.
2. Open a bug report.
3. Include Captail version, Windows version, GPU, driver version, source, codec, FPS, resolution, and reproduction steps.
4. Attach %APPDATA%\Captail\log.txt when possible. Review it first and remove personal paths or other sensitive information.

Requests for older NVIDIA, AMD, and Intel testing are welcome even when everything works.

Building from source

Requirements:

• Windows 10/11 x64
• .NET 9 SDK
• Visual Studio 2022 Build Tools with Desktop development with C++
• CMake 3.20+

git clone https://github.com/FaulMit/captail.git
cd captail
.\tools\AcquireObsRuntime.ps1
dotnet build .\Captail.sln -c Release

Create local release packages:

.\tools\BuildRelease.ps1 -Version 0.1.0 -InnoSetupCompiler "C:\Program Files\Inno Setup 7\ISCC.exe"

See CONTRIBUTING.md for development guidelines and docs/RELEASING.md for the automated release process.

Architecture

• ObsReplayEngine.cs — libobs lifecycle, sources, scene, encoders, and Replay Buffer.
• ObsNative.cs — focused P/Invoke bindings for libobs.
• native/ObsBridge — safe bridge for variadic OBS logging.
• native/ObsCaptureFixture — D3D11 fixture for Game Capture and high-FPS validation.
• App.xaml.cs — tray, hotkeys, notifications, single-instance behavior, watchdog, and recovery.
• SettingsWindow.* — compact WPF interface.

License and attribution

Captail is licensed under GNU GPL-2.0-or-later. See LICENSE.

Captail uses libobs and selected OBS Studio runtime components. See THIRD_PARTY_NOTICES.md.

Captail is not affiliated with or endorsed by NVIDIA or OBS Project. NVIDIA and ShadowPlay are trademarks of NVIDIA Corporation.