Getting 500 error when testing Zapier authentication trigger

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1

I’m trying to create a trigger that fires whenever a user logs into my application through Zapier. The authentication endpoint works perfectly when I test it using Postman, but Zapier keeps returning a 500 internal server error during trigger testing.

My authentication endpoint expects these headers and body parameters:

Headers:
{
    "org-id": "{{organization_id}}",
    "request-id": "{{request_id}}",
    "Authorization": "{{auth_token}}",
    "Client-id": "{{client_id}}"
}

Payload:
{
    "username": "{{user_email}}",
    "password": "{{user_password}}"
}

The same request structure works without issues in Postman, but fails consistently in Zapier. I’m wondering if there’s something specific about how Zapier handles the authentication flow that I’m missing. Any suggestions on what might be causing this discrepancy?

2

That 500 error is probably header formatting differences between Postman and Zapier. I hit this exact problem last year building a custom Zapier integration. Zapier sends headers with different casing or encoding, which breaks strict header validation on servers. Check if your auth endpoint is case-sensitive with header names - especially custom ones like “org-id” and “request-id”. Also see if Zapier’s auto-adding content-type headers that mess with your expected format. For me, the server rejected requests because Zapier sent “Content-Type: application/json; charset=utf-8” instead of just “application/json”. I had to make the server validation more lenient with header variations to fix the 500 errors.

3

This is probably a variable substitution problem in your Zapier request template. Those double-bracketed variables like {{organization_id}} and {{auth_token}} are likely showing up as empty strings or undefined values because they’re not mapped correctly in your trigger setup. I’ve hit this exact issue with webhook integrations - Zapier sends the literal string “{{variable_name}}” instead of the actual value, which kills authentication on the server. Check that all your variables are properly defined in the Zapier developer platform with sample data filled in. Make sure your trigger’s input fields match exactly with the variable names you’re using in headers and payload.

4

i’ve had similar issues before. sometimes zapier sends extra params that mess things up. def check your logs to see the exact req they are making. it might give u insight on the 500 error.