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What does ERR_NGROK_3004 mean?

ngrok returns ERR_NGROK_3004 with this message:

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Why does ngrok return ERR_NGROK_3004?

This error usually occurs when users are hosting a secure upstream service (https://localhost:[PORT]) but have not configured the ngrok agent to send HTTPS traffic to it.

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How do I fix ERR_NGROK_3004?

  • When starting the ngrok agent, use the full upstream service address. For example: ngrok http https://localhost:8081.

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Where can I get more help with ERR_NGROK_3004?

Email support@ngrok.com and include the error code.