ytdl-org/youtube-dl · error · IOError

file locking is not supported on this platform

Error message

file locking is not supported on this platform

What it means

Error "file locking is not supported on this platform" thrown in ytdl-org/youtube-dl.

Source

Thrown at youtube_dl/utils.py:3547

        if not UnlockFileEx(handle, 0,
                            whole_low, whole_high, f._lock_file_overlapped_p):
            raise OSError('Unlocking file failed: %r' % ctypes.FormatError())

else:
    # Some platforms, such as Jython, is missing fcntl
    try:
        import fcntl

        def _lock_file(f, exclusive):
            fcntl.flock(f, fcntl.LOCK_EX if exclusive else fcntl.LOCK_SH)

        def _unlock_file(f):
            fcntl.flock(f, fcntl.LOCK_UN)
    except ImportError:
        UNSUPPORTED_MSG = 'file locking is not supported on this platform'

        def _lock_file(f, exclusive):
            raise IOError(UNSUPPORTED_MSG)

        def _unlock_file(f):
            raise IOError(UNSUPPORTED_MSG)


class locked_file(object):
    def __init__(self, filename, mode, encoding=None):
        assert mode in ['r', 'a', 'w']
        self.f = io.open(filename, mode, encoding=encoding)
        self.mode = mode

    def __enter__(self):
        exclusive = self.mode != 'r'
        try:
            _lock_file(self.f, exclusive)
        except IOError:
            self.f.close()
            raise

View on GitHub (pinned to 956b8c5855)

Solutions

1. Run on a platform/filesystem that supports file locking, or avoid concurrent runs.

When it happens

Trigger: Thrown at youtube_dl/utils.py:3547 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of ytdl-org/youtube-dl@956b8c5855 (2026-08-14). Data as JSON: /api/errors/10cad890b37d6554. Report an issue: GitHub.