ytdl-org/youtube-dl · error · NotImplementedError
Unsupported property %r on %r
Error message
Unsupported property %r on %r
What it means
Error "Unsupported property %r on %r" thrown in ytdl-org/youtube-dl.
Source
Thrown at youtube_dl/swfinterp.py:599
idx = 0 if len(args) == 0 else args[0]
assert isinstance(idx, int)
res = ord(obj[idx])
stack.append(res)
continue
elif isinstance(obj, list):
if mname == 'slice':
assert len(args) == 1
assert isinstance(args[0], int)
res = obj[args[0]:]
stack.append(res)
continue
elif mname == 'join':
assert len(args) == 1
assert isinstance(args[0], compat_str)
res = args[0].join(obj)
stack.append(res)
continue
raise NotImplementedError(
'Unsupported property %r on %r'
% (mname, obj))
elif opcode == 71: # returnvoid
res = undefined
return res
elif opcode == 72: # returnvalue
res = stack.pop()
return res
elif opcode == 73: # constructsuper
# Not yet implemented, just hope it works without it
arg_count = u30()
args = list(reversed(
[stack.pop() for _ in range(arg_count)]))
obj = stack.pop()
elif opcode == 74: # constructproperty
index = u30()
arg_count = u30()
args = list(reversed(View on GitHub (pinned to 956b8c5855)
Solutions
- Update youtube-dl; the SWF uses an unsupported property.
When it happens
Trigger: Thrown at youtube_dl/swfinterp.py:599 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/32a50e499d088589.
Report an issue: GitHub.