Why does a POST request to my webhook in Webflow open a new tab and display the JSON response instead of showing a success message within Webflow?

A POST request opening a new tab and showing a JSON response instead of staying inside Webflow usually means the form’s action handling is incorrectly configured or not using AJAX.

1. Webflow Forms Expect Webflow-Handled Submissions

• Webflow forms are designed to submit data to Webflow’s servers by default.
• If a custom form action is added (like a webhook URL), it overrides Webflow’s native behavior.
• Submitting to an external URL without additional configuration causes the browser to perform a full POST request, which results in the response being opened in a new tab or rerendered in the current window.

2. Why the JSON Response Displays in a New Tab

• When a form's action points to a webhook (e.g., Zapier, Integromat, custom server), the browser sends the POST request normally.
• If the webhook returns a JSON response with a content-type like application/json, the browser doesn't know how to handle it visually, so it renders the raw JSON in a new tab.
• Unlike Webflow’s built-in system, there's no built-in success/failure message handler for forms that bypass Webflow.

3. How to Fix It

To ensure the user sees a success message after submission, without a new tab:

• Use AJAX via Webflow's default form behavior: Leave the action field of the form blank. Then use Webflow Logic, native integrations, or hidden fields and automation tools to handle the data.
• If using a custom webhook (like Zapier):
• Remove the action attribute from the form so Webflow handles the submission.
• Create an integration inside Webflow (e.g., Logic or using tools like Make.com) to send the submission to your endpoint.
• Alternative: Use custom JavaScript to handle form submission via fetch or XMLHttpRequest asynchronously, then show a confirmation message in the DOM manually.

4. Use Webflow Logic or Third-Party Tools

• Webflow Logic allows native form handling and conditional workflows, including sending data to external APIs.
• Tools like Zapier or Make.com can be integrated using webhooks triggered from Webflow submissions — without overriding the form's submission behavior.

Summary

The issue happens because you're overriding Webflow’s default form behavior by setting a direct webhook action, which causes a full POST and browser-rendered JSON. Remove the action attribute, use Webflow’s native form submission, and integrate external handling via Webflow Logic or asynchronous JavaScript to keep the experience inside Webflow.