Facebook CAPI 400 Bad Request Fix for Make.com

This deployment guide shows how to instantly fix the Facebook Conversions API integration error when building a custom server-side tracking system in Make.com, including resolving invalid parameter issues, fixing payload formatting, and accurately hashing your tracking events.

Meta’s Conversions API strictly validates every single HTTP POST request. This usually happens after operators blindly copy payload examples generated by ChatGPT without understanding array structures. Here is the exact fix.

Why You Get a Facebook CAPI 400 Error

If you check your HTTP module output inside Make.com, you are likely seeing this exact error response from the Meta Graph API endpoint:

{
  "error": {
    "message": "Invalid parameter",
    "type": "OAuthException",
    "code": 100,
    "error_subcode": 2804019,
    "is_transient": false,
    "error_user_title": "Missing required parameter",
    "error_user_msg": "A required parameter is missing from your request."
  }
}

Because Facebook’s server could not parse your data, the request dies. The most common triggers are:

• Invalid JSON structure: Missing the mandatory data array wrapper around your event object.
• Unhashed PII: Sending raw emails instead of SHA-256 formatted hashes, or failing to normalize the string first.
• Wrong event_time format: Sending standard dates instead of a 10-digit UNIX timestamp.

The Quick Fix (Valid JSON Payload)

Copy and paste this exact structure into your Make.com HTTP module’s “Request content” field. Notice that the event is strictly wrapped inside the data array.

{
  "data": [
    {
      "event_name": "Purchase",
      "event_time": {{formatDate(now; "X")}},
      "action_source": "website",
      "user_data": {
        "em": ["{{sha256(lower(trim(1.email)); "hex")}}"],
        "ph": ["{{sha256(1.phone; "hex")}}"],
        "client_ip_address": "{{1.ip_address}}",
        "client_user_agent": "{{1.user_agent}}"
      },
      "custom_data": {
        "currency": "USD",
        "value": {{1.purchase_value}}
      }
    }
  ]
}

Step-by-Step Fix (Make.com Context)

Step 1: Check Your HTTP Module Headers

Ensure your Make.com “Make a request” HTTP module is configured exactly like this:

• URL: https://graph.facebook.com/v19.0/{{YOUR_PIXEL_ID}}/events?access_token={{YOUR_ACCESS_TOKEN}}
• Method: POST
• Headers: Add a header with Key: Content-Type and Value: application/json

Correct mapping for the Make.com HTTP module pointing to the Graph API.

Step 2: Fix Payload Mapping & Hashing

Inside the JSON structure, you cannot pass a raw email address. To satisfy Meta’s Event Match Quality (EMQ) standards, you must use Make.com’s native string functions to normalize the data (lowercase and trim whitespace) before hashing it.

Use this exact formula syntax in Make.com for the email field: {{sha256(lower(trim(1.email)); "hex")}}

Step 3: Validate Your UNIX Timestamp

The event_time parameter must be a 10-digit UNIX timestamp. Use Make.com’s {{formatDate(now; "X")}} function to convert the current execution time into a compliant UNIX string.

Common Mistakes Checklist

Before running your scenario again, verify you haven’t made these typical operator errors:

Advanced Operator Diagnostics: Still Getting a 400?

If you have corrected the JSON wrapper and hashed the PII but the HTTP module is still failing, check these deeper structural issues:

• Case-Sensitive Event Names: Meta requires standard events to be capitalized. Sending "event_name": "purchase" will fail. It must be "Purchase".
• Stale Access Token: The System User access token generated inside Meta Business Manager does not last forever unless explicitly set to never expire. Check if your token was revoked.
• Stray Test Codes: If you mapped a test_event_code during testing but left it in the payload for a live production environment, Meta will frequently reject the request.

How to Test the Payload

Do not test blindly in production. Open your Meta Events Manager, click on your Pixel, and navigate to the Test Events tab. Copy your unique test_event_code.

Add this code to your JSON payload right beneath the action_source line like this: "test_event_code": "TEST81014",. Run the Make.com module. You can also verify your JSON structure using the official Meta Payload Helper.

A successful test inside Meta Events Manager confirming valid server-side event tracking.

If the payload is correct, the module will turn green and return an HTTP 200 OK status code, completely resolving the Facebook CAPI 400 Bad Request Make.com integration issue.

Frequently Asked Questions