I’m trying to set up a Slack integration using Zapier to monitor when someone replies to a message. I need to listen for the message_replied event through Slack’s Events API.
The problem is that Slack requires URL verification before you can start receiving events. During this verification process, Slack sends a POST request with a challenge parameter that your endpoint needs to echo back immediately. However, Zapier’s webhook system doesn’t seem capable of handling this verification step properly.
I keep getting this error message: “Request URL Your URL didn’t respond with the value of the challenge parameter.”
Has anyone found a way to work around this limitation? I’m using the “Webhooks by Zapier” app with the “Catch Hook” trigger, and I have Event Subscriptions enabled in my Slack bot configuration.
Any suggestions would be helpful!
totally feel u, that webhook thing can be a pain! i did somethin similar, just setup ngrok for local testing and had it echo back the challenge. then swaped it once slack verified. really helps!
Yes, this is a frequent challenge when trying to integrate Slack’s Events API with Zapier. The crux of the problem lies in Zapier’s webhooks being designed for asynchronous handling, while Slack mandates an immediate response for challenge verification. I’ve faced this issue myself when I was setting up event monitoring. What worked well for me was creating a lightweight AWS Lambda function dedicated solely to responding to Slack’s challenge. This function captures the challenge parameter and immediately sends it back to Slack, and afterwards, it passes verified events onto Zapier for processing. The Lambda function is straightforward - it simply checks for the challenge and echoes it back. Once the verification is successful, everything falls into place for managing your event flow through Zapier.
You’ve hit a fundamental limitation with Zapier’s webhook setup. The Catch Hook trigger works asynchronously, but Slack’s challenge verification needs an immediate synchronous response with the exact challenge value. I ran into this exact problem last year building a similar integration. I ditched Zapier for the initial webhook endpoint and used a simple cloud function instead. I deployed a basic Node.js function on Vercel that handles challenge verification, then forwards actual events to Zapier using their webhook URL. The verification handler is just a few lines of code - checks if the request has a challenge parameter and returns it immediately. Once verified, you can process real events through your existing Zapier workflow. This worked perfectly for my message monitoring setup.
I Tried doing it and it always says the url didnt respond I am literally Struck