How can I avoid duplicate CRM HTTP requests when splitting a webhook array in n8n?

Below is one approach that helped others avoid the duplicate CRM data problem when splitting items from a webhook.

What’s Happening

When you split the webhook data early in the workflow, every one of the 16 split items goes down the branch that calls your CRM. That means the HTTP Request node that fetches CRM data gets executed 16 times, so you end up with the same array 16 times. Alternatively, if you delay splitting until after the HTTP Request, the webhook data is still in array form and not available as individual items, which causes errors during later processing.

A Possible Solution

To avoid duplication and errors, you can structure your workflow so that your CRM HTTP Request runs only once (retrieving the full array just one time) and then make that data available for every webhook item that is split later. Here’s how:

1. Do not split the webhook data immediately.
   Start with your webhook node that receives the 16-object array.

2. Branch the workflow:
   • On one branch, pass the webhook data as is to an HTTP Request node to get your CRM data. Make sure that if possible you have the CRM HTTP Request node set to "Run Once For All Items" (or use another method that prevents duplicate calls).
   • On the other branch, keep the same webhook data intact and split it later.

3. Merge the Data:
   Once you have:

   • The full CRM array from your HTTP Request (which ran only once)
   • The individual items from your webhook after splitting using a node like Loop Over Items (or Split In Batches)

   Use the Merge node (or Join) to combine each individual webhook item with the CRM data. Since the CRM branch ran only once, each webhook item will be supplemented with a single instance of the CRM array.

Key Points

• Avoid Early Splitting for Shared Data: Splitting the webhook too early means that any subsequent HTTP Request will be repeated per item. Instead, run that HTTP Request once on the overall (unsplit) array.
• Utilize Merge/Join: The Merge node lets you combine data from different branches (one with split items and one with the shared CRM response) without repeating the CRM data.
• Node Configuration:
  • Check for a “Run Once For All Items” option on your HTTP Request node if available.
  • Consider using the Loop Over Items node (or Split In Batches node) after you’ve obtained the CRM data so that each split item can be merged correctly with the CRM output.

Using this structure, you’ll end up with only one CRM array per webhook request and then 16 individual items from the webhook, each merged with that single CRM data set—thus avoiding both duplication and splitting errors.

Give this approach a try in your workflow. Let me know if you need further clarification on any of the steps!