Slack URL Verification Fails on Production URL, but Works with Test URL

[f.sude]

Hello,

I am having a persistent challenge_failed error when trying to verify a webhook URL for a Slack app. I believe this is a platform issue and not a workflow configuration error.

Here is what I have confirmed:

1. My workflow is very simple: Webhook Node → Respond to Webhook Node.

2. The Respond to Webhook node is correctly configured to return the challenge. I have tried both JSON response {"challenge":"{{$json.body.challenge}}"} and Text response {{$json.body.challenge}}.

3. Most importantly: When I use a curl command to test the Test URL, the workflow works perfectly and returns the challenge string to my terminal as expected.

4. However, when Slack tries to verify the Production URL, it always fails with a challenge_failed error. The execution log in n8n for this attempt shows a “Succeeded” run, but Slack does not accept the response.

This proves that my workflow logic is correct. The issue seems to be specific to the communication between Slack and my n8n Production URL.

Thanks in advance.

[darrell_tw]

If you are talking about the Event Subsription

You can just use n8n slack trigger’s production url. It will solve the challenge parameter automatically.