Loop

Iterate through body nodes multiple times

Overview

Iteratively executes a sub-workflow defined by all nodes between this Loop node and its paired Loop End node. Supports three iteration modes: forEach (once per input item), fixedCount (N iterations), and whileCondition (repeat while an expression evaluates to truthy). Each iteration runs the body as a nested workflow execution. The loop body’s output can be accumulated across iterations or passed through independently. In forEach mode, optional batching groups input items into chunks with a configurable delay between batches for rate limiting. A Loop never creates a graph cycle — the body runs as a nested execution rather than a backward edge on the canvas.

Category: Core Nodes
Tool Name: loop
Version: 1

Appearance: Icon: loop | Color: #8b5cf6

Node Type

Action — processes input items and produces output

Input / Output

Direction	Port(s)
Input	Input
Output	Done, Error

Credentials

This tool does not require any credentials.

Parameters

Parameter	Type	Required	Default	Description
Mode	options	Yes	forEach	How the loop determines when to iterate.
				Options: forEach (execute the loop body once for each input item), fixedCount (execute the loop body a fixed number of times), whileCondition (execute the loop body while a condition is true)
Iterations	number	Yes	10	Number of times to execute the loop body. (shown when Mode is fixedCount)
Condition	string	Yes	{{ $json.continue === true }}	Expression that is evaluated after each iteration. The loop continues while this evaluates to a truthy value. Has access to $json (current item), $iteration (0-based index), and $accumulator (array of all prior outputs). (shown when Mode is whileCondition)
Max Iterations (Safety Limit)	number	No	100	Maximum number of iterations allowed, regardless of mode. Prevents runaway loops. Applies to all modes as a safety ceiling.
Accumulation Strategy	options	No	lastOnly	How iteration results are accumulated for the final output.
				Options: lastOnly (output only the final iteration’s results), all (concatenate outputs from every iteration)
Max Concurrency	number	No	1	Max concurrent items to process. Default is 1 (sequential iteration). Values > 1 are only meaningful in forEach mode with independent iterations.
Enable Batching	boolean	No	false	Group input items into batches. Each iteration processes a batch instead of a single item. (shown when Mode is forEach)
Batch Size	number	Yes	10	Number of items per batch. (shown when Mode is forEach and Enable Batching is true)
Delay Between Batches (ms)	number	No	0	Milliseconds to wait between batches. Useful for rate limiting. No delay is applied before the first batch. Set to 0 for no delay. (shown when Mode is forEach and Enable Batching is true)

Output Data

The Done port emits the accumulated results of the loop: the last iteration’s items when Accumulation Strategy is lastOnly, or every iteration’s items concatenated when it is all. The items are whatever the last node of the loop body produced, so their shape is defined by the body, not by this node. When the error mode is errorPort, an iteration that fails emits an error item on the Error port and the loop carries on with the next iteration.

Every item handed to the loop body carries a _loopMeta object alongside its own JSON:

• iteration — 0-based index of the current iteration
• itemIndex — position of the item within this iteration’s input
• mode — the iteration mode in use
• batchIndex, batchSize, batchItemIndex, totalBatches — added only when batching is enabled

Read it inside the body with expressions such as {{ $json._loopMeta.iteration }}.

If there are no nodes between the Loop and its Loop End, the node passes its input straight through to Done.

Usage Examples

• Loop through each item and enrich with API calls
• Repeat a transformation 5 times to refine output
• Keep calling an LLM until the output passes validation

Example Configuration

Run the body once per input item, with a safety ceiling:

{ "type": "loop", "parameters": { "mode": "forEach", "maxIterations": 100 } }

Error Handling

Mode	Behavior
stop	Halts workflow on first error
continue	Skips failed items, passes successful ones through
errorPort	Routes failed items to Error output port

Tips

Iteratively executes body nodes between Loop and Loop End — supports forEach, fixedCount, and whileCondition modes.

Behavior notes

• Pair every Loop with a Loop End. The nodes chained between the two are the loop body; the Loop End marks where the body stops.
• Max Iterations is a hard ceiling for every mode, including fixedCount — raise it above the iteration count you actually want.
• whileCondition is evaluated after each iteration, so the body always runs at least once.
• Batching changes what an iteration is. With batching on, one iteration processes a whole batch instead of a single item, and Delay Between Batches applies between iterations — never before the first one.