Tyrrrz/YoutubeDownloader · error · PlatformNotSupportedException

Unsupported operating system.

Error message

Unsupported operating system.

What it means

Thrown by the local GetSystemMoniker() inside FFmpeg.GetDownloadUrl() while auto-provisioning the FFmpeg binary. The library downloads a prebuilt FFmpeg from github.com/Tyrrrz/FFmpegBin (URL built at FFmpeg.cs:110) and only ships assets for Windows, Linux, and macOS; any other OS cannot be mapped to a release-asset suffix, so the URL cannot be constructed and PlatformNotSupportedException is thrown.

Source

Thrown at YoutubeDownloader.Core/Downloading/FFmpeg.cs:88

        GetProbeDirectoryPaths()
            .Distinct(StringComparer.Ordinal)
            .Select(dirPath => Path.Combine(dirPath, CliFileName))
            .FirstOrDefault(File.Exists);

    private static string GetDownloadUrl()
    {
        static string GetSystemMoniker()
        {
            if (OperatingSystem.IsWindows())
                return "windows";

            if (OperatingSystem.IsLinux())
                return "linux";

            if (OperatingSystem.IsMacOS())
                return "osx";

            throw new PlatformNotSupportedException("Unsupported operating system.");
        }

        static string GetArchitectureMoniker()
        {
            if (RuntimeInformation.ProcessArchitecture == Architecture.X64)
                return "x64";

            if (RuntimeInformation.ProcessArchitecture == Architecture.X86)
                return "x86";

            if (RuntimeInformation.ProcessArchitecture == Architecture.Arm64)
                return "arm64";

            throw new PlatformNotSupportedException(
                $"Unsupported architecture: {RuntimeInformation.ProcessArchitecture}."
            );
        }

View on GitHub (pinned to bbcff03951)

Solutions

1. Install FFmpeg and make it resolvable via PATH (or place it in AppContext.BaseDirectory) so TryGetCliFilePath() returns a path and DownloadAsync is never called.
2. Pass ffmpegPath explicitly to VideoDownloader.DownloadVideoAsync(...) to bypass auto-download (FFmpeg.cs:77 falls back to it).
3. If you must support the platform, extend GetSystemMoniker() with the OS moniker and ensure a matching asset exists in the FFmpegBin release at Version (currently "8.1").

Example fix

// before: relies on auto-download, which throws on unsupported OS
await FFmpeg.DownloadAsync(outputPath, progress, ct);

// after: only auto-download on supported platforms, otherwise require a system binary
var ffmpeg = FFmpeg.TryGetCliFilePath();
if (ffmpeg is null)
{
    if (!OperatingSystem.IsWindows() && !OperatingSystem.IsLinux() && !OperatingSystem.IsMacOS())
        throw new InvalidOperationException("Install FFmpeg manually on this OS.");
    await FFmpeg.DownloadAsync(outputPath, progress, ct);
    ffmpeg = outputPath;
}

static bool IsFfmpegAutoDownloadSupported() =>
    OperatingSystem.IsWindows() || OperatingSystem.IsLinux() || OperatingSystem.IsMacOS();

// before calling FFmpeg.DownloadAsync:
if (!IsFfmpegAutoDownloadSupported() && FFmpeg.TryGetCliFilePath() is null)
{
    // instruct the user to install FFmpeg manually instead of auto-downloading
}

try
{
    await FFmpeg.DownloadAsync(outputPath, progress, ct);
}
catch (PlatformNotSupportedException ex) when (ex.Message == "Unsupported operating system.")
{
    // prompt the user to install FFmpeg in PATH, or accept an explicit ffmpegPath
}

When it happens

Trigger: Calling FFmpeg.DownloadAsync(...) on a runtime where OperatingSystem.IsWindows(), IsLinux(), and IsMacOS() all return false (e.g. FreeBSD, Solaris). It is only reached when no FFmpeg was found by TryGetCliFilePath() and the caller falls through to auto-download.

Common situations: Running under Wine/Proton or a translation layer that reports a non-standard OS; niche containers/distros; new .NET platforms added later. Note TryGetCliFilePath() probes AppContext.BaseDirectory, the current directory, and PATH (plus registry PATH on Windows), so a system FFmpeg avoids this path entirely.

Related errors

• Unsupported architecture: {RuntimeInformation.ProcessArchite
• Entry '{CliFileName}' not found in the downloaded archive.

AI-assisted analysis of Tyrrrz/YoutubeDownloader@bbcff03951 (2026-08-13). Data as JSON: /api/errors/e0823269f8c42aad. Report an issue: GitHub.