Error interpreting player js: https://youtube.com/s/player/f4d92f0b/player_ias.vflset/en_US/base.js and 403

[gr33tx]

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🐞 Bug Description

Error interpreting player js: https://youtube.com/s/player/f4d92f0b/player_ias.vflset/en_US/base.js reason: Expecting value: line 1 column 1 (char 0)
And after that I get HTTP Error 403: Forbidden - even with proxy, which did not used for 5 days, even with CLI, not Flask.
I don't know what is the reason, but I get HTTP Error 403: Forbidden often and often.

🔢 Code Snippet

Include the minimal code snippet that reproduces the issue.

While getting this video: https://youtube.com/watch?v=8rypermH5p4

client = 'web'

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🎯 Expected Behavior

Describe what you expected to happen instead of the observed behavior.

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📸 Screenshots or Logs

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🖥️ Environment Details

Python 3.9
Pytubefix 10.3.8

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📋 Additional Context

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🚀 Next Steps

Once submitted, we will triage the issue. Make sure to respond to follow-up questions to keep the process smooth.

[mgnegypt]

I have the same problem and don’t know what the solution is. I hope someone can help us and provide a solution to this issue.

[NannoSilver]

I am getting a similar problem, but for a different player ID:
Error interpreting player js: https://youtube.com/s/player/4a6035e3/player_ias.vflset/en_US/base.js reason: Expecting value: line 1 column 1 (char 0)

[Muggwomp]

Hey all, after feeding ChatGPT-5.4 Codex the 4a6035e3 player base.js and the current patched cipher from SzeMeng76 and telling the machine to fix it, I seem to have a working cipher.py. I tested a hundred or so video downloads and all were 100% successful (I won't guarantee it's going to be successful for everyone or 100% of the time since YouTube changes things every 1-2 weeks it now seems). I know how some feel about that which is AI coded, so I just made the file's own repository [https://github.com/Muggwomp/pytubefix-cipher-patch] and you can do whatever you want with it.

[gr33tx]

Hey all, after feeding ChatGPT-5.4 Codex the 4a6035e3 player base.js and the current patched cipher from SzeMeng76 and telling the machine to fix it, I seem to have a working cipher.py. I tested a hundred or so video downloads and all were 100% successful (I won't guarantee it's going to be successful for everyone or 100% of the time since YouTube changes things every 1-2 weeks it now seems). I know how some feel about that which is AI coded, so I just made the file's own repository [https://github.com/Muggwomp/pytubefix-cipher-patch] and you can do whatever you want with it.

Interesting! It works! Thanks! But I got another error: Error interpreting player js: https://youtube.com/s/player/8c57fc20/player_ias.vflset/en_US/base.js reason: {'error': "Cannot read properties of undefined (reading 'length')", 'stack': "TypeError: Cannot read properties of undefined (reading 'length')\n at H_ (evalmachine.<anonymous>:6320:379)\n at Socket.<anonymous>

[Muggwomp]

Told the machine to fix the error you encountered for player 8c57fc20. It says it has and I have to take it at its word since I haven't encountered that particular player. I put the updated cipher.py in the same place as the last one.

[gr33tx]

Told the machine to fix the error you encountered for player 8c57fc20. It says it has and I have to take it at its word since I haven't encountered that particular player. I put the updated cipher.py in the same place as the last one.

Thank you! It works! I get another error:
Error interpreting player js: https://youtube.com/s/player/8c83ec2e/player_ias.vflset/en_US/base.js reason: {'error': "Cannot read properties of undefined (reading 'undefined')", 'stack': "TypeError: Cannot read properties of undefined (reading 'undefined')\n at VO (evalmachine.<anonymous>:2762:395)\n at Socket.<anonymous>

[Muggwomp]

Patched for player 8c83ec2e. And for future errors, unless it's something completely different than an "interpreting player..." error, you can just give the player name instead of printing the whole output.

[NannoSilver]

Patched for player 8c83ec2e. And for future errors, unless it's something completely different than an "interpreting player..." error, you can just give the player name instead of printing the whole output.

Can you submit as a Poll Request?
That will allow to better visualize the differences and eventually merge with the main branch with the credits for you.

[gr33tx]

Hi! Another one: player 5a9b5eed

[Muggwomp]

Patched. Interestingly, Codex said that while the player was already accounted for, there was a slight variant of the same player that it took care of.

@NannoSilver Do you want me to still do that pull request, or should I wait until gr33tx finds all the players that need to be patched 😁?

[NannoSilver]

Patched. Interestingly, Codex said that while the player was already accounted for, there was a slight variant of the same player that it took care of.

@NannoSilver Do you want me to still do that pull request, or should I wait until gr33tx finds all the players that need to be patched 😁?

YouTube is releasing new players almost daily.

Ideally, we should aim for a solution that covers all cases, with one or multiple fallbacks. One possible fallback could be similar to what was proposed in PR #584. While it may be somewhat fragile, it could still work.

In any case, presenting this in the format of a Pull Request would make the changes more organized and easier to visualize in the code.