Aggregate Multiple Items into a Single Summary Using the Aggregate Node

In n8n, the Aggregate node combines many separate items into one item — turning a stream of records into a single array you can pass on as one payload. Use All Item Data to bundle whole items together, or Individual Fields to pull one field from every item into a flat list. It is the inverse of the Split Out node.

What does the n8n Aggregate node do?

It collapses multiple incoming items into a single output item. Instead of 15 records flowing downstream separately, the Aggregate node wraps their data into one item — ideal for building a summary, a report, or a single API or email payload.

How do you combine multiple items into one in n8n?

Add an Aggregate node and choose a mode:

• All Item Data — keep whole items together as an array of objects.
• Individual Fields — extract one named field from every item into a flat list. Turn on Merge Lists to output a single flat list instead of a list of lists.

Worked example: a workflow processes 15 order line items individually (for inventory checks), then combines them into one confirmation email.

Setting	Value
Aggregate	Individual Fields
Input Field	product_name → Output: products
Input Field	line_total → Output: amounts

// Input — 3 items:
{ "product_name": "Widget A", "line_total": 29.99, "qty": 2 }
{ "product_name": "Widget B", "line_total": 49.99, "qty": 1 }
{ "product_name": "Widget C", "line_total": 15.00, "qty": 5 }

// Aggregated output — 1 item:
{
  "products": ["Widget A", "Widget B", "Widget C"],
  "amounts": [29.99, 49.99, 15.00]
}

Follow up with a Code node to build the email body:

const products = $json.products;
const amounts = $json.amounts;
const total = amounts.reduce((sum, val) => sum + val, 0);

let body = "Order Summary:\n\n";
for (let i = 0; i < products.length; i++) {
  body += `- ${products[i]}: $${amounts[i].toFixed(2)}\n`;
}
body += `\nTotal: $${total.toFixed(2)}`;

return [{ json: { emailBody: body, orderTotal: total } }];

Aggregate vs Split Out: what is the difference?

Node	What it does	Items in → out
Aggregate	Combines many items into one	Many → 1
Split Out	Splits one item's list into many items	1 → many

They are opposites: use Split Out to fan a list into separate items, and Aggregate to gather them back together.

When should you aggregate items into a batch?

• Building one API request (a batch payload) from many records.
• Composing a single email or report from loop results.
• Producing a summary object after a Split in Batches loop.
• Reducing many items to one before a final write or notification.

Related: Split one item into many (Split Out) · Process large datasets in batches (Split in Batches) · Enrich records with the Merge node