What could be causing the recurring 400 status code in my Webflow flow test?
TL;DR
- Check that all input data is correctly formatted and matches expected types for fields and APIs.
- Ensure the webhook or API URL, headers, and authentication are accurate.
- Verify CMS fields are properly populated and meet Webflow's data constraints.
- Inspect flow trigger payloads and variable values using “Test in Flow”.
- Validate all conditional logic paths and run manual tests to compare successful vs. failing runs.
- Review external server logs for more detailed error explanations if using third-party APIs.
A 400 status code in your Webflow flow test typically indicates a “Bad Request,” meaning the request your flow is sending is malformed or rejected by the receiving server.
1. Verify Input Data Formatting
- A 400 error often means the data being sent is invalid or doesn't match what the receiving API or endpoint expects.
- Check for issues like:
- Missing required fields.
- Incorrect data types (e.g., sending text where a number is expected).
- Malformed email addresses, URLs, or JSON structures.
2. Check Webhook or API Integration Details
- If your Webflow Flow is using a webhook or third-party integration, make sure:
- The URL is correct and HTTPS is used.
- The headers are properly configured (e.g., correct
Content-Type). - Any authentication (API keys, tokens) are correctly formatted and passed.
3. Validate Collection Field Bindings
- If the flow interacts with a CMS collection item, verify that:
- Required CMS fields are not empty or null.
- The data you're inserting or updating conforms to Webflow's collection constraints (e.g., character limits, field types).
4. Review Flow Trigger Payload
- Look at the data being passed from the trigger (e.g., "Form submission", "CMS item created").
- Use the “Test in Flow” feature to view raw payloads and confirm field coverage.
5. Inspect Conditional Logic or Variables
- If your flow has conditional logic, make sure all conditions are met properly before a step executes.
- Sometimes variables passed between steps may be undefined or invalid, especially after API calls.
6. Try Manually Running the Flow
- Use the Test Flow button with a known-good input to isolate the issue.
- Compare successful and failing flow runs to find discrepancies in payloads or headers.
7. Check Receiving Server Logs (If Hosted Externally)
- If you're hitting an external API or custom backend, check the server logs or API response.
- Some services return detailed 400 error messages in their response body, but Webflow’s UI may not display them fully.
Summary
A 400 status code in Webflow flows is typically due to wrong or incomplete data, improper API setup, or misconfigured logic. Review your flow’s data inputs, headers, and external endpoints to identify and correct the malformed request.