Passing Data Between Steps

One of the most powerful features in Activepieces is the ability to pass data between steps. This guide explains how to reference step outputs, use expressions, and map data throughout your workflow.

Understanding Step Outputs

Every step in your workflow produces an output that subsequent steps can access. The output structure depends on the step type.

Accessing Step Outputs

Use the mustache syntax {{ stepName.property }} to reference data from previous steps:

// If you have a step named "get_user" that returns:
{
  "id": "123",
  "name": "John Doe",
  "email": "john@example.com"
}

// Access the data in later steps:
{{ get_user.name }}          // "John Doe"
{{ get_user.email }}         // "john@example.com"
{{ get_user.id }}            // "123"

Step names are automatically generated as step_1, step_2, etc., but you can rename them to something more meaningful like get_user or send_email.

Variable Types

Activepieces supports several types of variables you can use in your workflows:

1. Step Outputs

Access data from any previous step:

{{ trigger.body.name }}           // Data from the trigger
{{ send_http.body.results }}      // HTTP response data
{{ transform_data.output }}        // Code action output

2. Loop Variables

When inside a loop, access iteration data:

// From packages/server/engine/test/handler/flow-looping.test.ts
{
  "type": "LOOP_ON_ITEMS",
  "settings": {
    "items": "{{ [4, 5, 6] }}"  // Array to iterate over
  },
  "firstLoopAction": {
    "name": "process_item",
    "settings": {
      "input": {
        "currentItem": "{{ loop.item }}",   // Current item
        "index": "{{ loop.index }}",         // Current index (1-based)
        "iteration": "{{ loop.iterations }}" // All iterations
      }
    }
  }
}

loop.item

The current item being processed

loop.index

Current iteration number (1-based)

loop.iterations

Array of all completed iterations

3. Connections

Reference saved connection credentials:

{{ connections.my_database.host }}
{{ connections.my_database.username }}

4. Router/Branch Data

Access branch evaluation results:

// Router output from packages/server/engine/test/handler/flow-branching.test.ts
{
  "router": {
    "output": {
      "branches": [
        {
          "branchIndex": 1,
          "branchName": "Test Branch",
          "evaluation": true  // Condition result
        }
      ]
    }
  }
}

Using Expressions

Activepieces supports JavaScript expressions within the mustache syntax:

String Operations

// Concatenation
{{ trigger.firstName + " " + trigger.lastName }}

// Template literals
{{ `Hello, ${trigger.name}!` }}

// String methods
{{ trigger.email.toLowerCase() }}
{{ trigger.name.toUpperCase() }}
{{ trigger.text.substring(0, 10) }}

Number Operations

// Arithmetic
{{ trigger.price * 1.1 }}           // Add 10%
{{ trigger.quantity + 5 }}
{{ (trigger.total - trigger.discount).toFixed(2) }}

// Comparisons
{{ trigger.age >= 18 }}
{{ trigger.score > 100 }}

Array Operations

// Map, filter, and more
{{ trigger.items.map(item => item.name) }}
{{ trigger.users.filter(user => user.active) }}
{{ trigger.numbers.reduce((sum, n) => sum + n, 0) }}

// Array access
{{ trigger.items[0] }}              // First item
{{ trigger.items.length }}          // Array length

Object Operations

// Access nested properties
{{ trigger.user.profile.address.city }}

// Spread operator
{{ { ...trigger.user, updated: true } }}

// Object methods
{{ Object.keys(trigger.data) }}
{{ Object.values(trigger.metadata) }}

Data Mapping Examples

Example 1: Transform API Response

HTTP Request Step

A step named fetch_users makes an API call:

{
  "status": 200,
  "body": {
    "users": [
      {"id": 1, "name": "Alice", "active": true},
      {"id": 2, "name": "Bob", "active": false},
      {"id": 3, "name": "Charlie", "active": true}
    ]
  }
}

Filter Active Users

Create a code action to filter:

export const code = async (inputs) => {
  const users = inputs.allUsers;
  return users.filter(user => user.active);
};

Input configuration:

{
  "allUsers": "{{ fetch_users.body.users }}"
}

Use Filtered Data

Reference the filtered results:

{{ filter_users.output }}  // [{id: 1, name: "Alice", ...}, ...]

Example 2: Loop Over Items

// Loop configuration from test suite
{
  "name": "process_orders",
  "type": "LOOP_ON_ITEMS",
  "settings": {
    "items": "{{ fetch_orders.body.results }}"  // Array from previous step
  },
  "firstLoopAction": {
    "name": "send_confirmation",
    "type": "PIECE",
    "settings": {
      "pieceName": "@activepieces/piece-gmail",
      "actionName": "send_email",
      "input": {
        "to": "{{ loop.item.customer.email }}",
        "subject": "Order #{{ loop.item.orderNumber }} Confirmed",
        "body": "Thank you for order #{{ loop.index }}!"
      }
    }
  }
}

Example 3: Conditional Data

Use ternary operators for conditional values:

// Set priority based on score
{{ trigger.score > 80 ? 'High' : trigger.score > 50 ? 'Medium' : 'Low' }}

// Default values
{{ trigger.name || 'Unknown' }}
{{ trigger.count ?? 0 }}

Testing Data Flow

When you test a workflow, you can inspect data at each step:

Test Flow
View Step Output
Debug Issues

Click Test Flow to run your workflow with sample data.

// From packages/web/src/app/builder/flow-canvas/widgets/test-flow-widget.tsx
const { mutate: runFlow } = flowHooks.useTestFlowOrStartManualTrigger({
  flowVersionId: flowVersion.id,
  onUpdateRun: (response) => {
    // Each step's output is captured
    const steps = response.flowRun.steps;
    // { step_1: {output: ...}, step_2: {output: ...} }
  }
});

Click on any executed step to see:

Input values that were used
Output data that was produced
Execution time and status

// Step output structure
{
  "status": "SUCCEEDED",
  "output": {
    // Actual step output data
  },
  "input": {
    // Input values used
  },
  "duration": 1250  // milliseconds
}

If data isn’t flowing correctly:

Check step names are correct
Verify the step executed successfully
Inspect the actual output structure
Ensure property paths are correct

Common mistake: Using {{ trigger.name }} when the trigger output is {{ trigger.body.name }}

Sample Data

Steps can save sample data for testing:

// From packages/shared/src/lib/automation/flows/actions/action.ts
export const SampleDataSetting = {
  "sampleDataFileId": string,       // Saved sample output
  "sampleDataInputFileId": string,  // Saved sample input
  "lastTestDate": string,           // When last tested
  "currentSelectedData": object     // Current test data
}

Sample data is automatically saved when you test individual steps, making it easy to test downstream steps without re-running the entire flow.

Advanced Data Techniques

Working with JSON

// Parse JSON string
{{ JSON.parse(trigger.jsonString) }}

// Stringify object
{{ JSON.stringify(trigger.data) }}

// Pretty print
{{ JSON.stringify(trigger.data, null, 2) }}

Date and Time

// Current timestamp
{{ Date.now() }}

// Format date
{{ new Date(trigger.timestamp).toISOString() }}

// Date arithmetic
{{ new Date(Date.now() + 86400000).toISOString() }}  // Tomorrow

Error Handling in Expressions

// Safe property access
{{ trigger?.user?.profile?.email || 'no-email@example.com' }}

// Try-catch in code actions
export const code = async (inputs) => {
  try {
    return JSON.parse(inputs.data);
  } catch (error) {
    return { error: error.message };
  }
};

Common Patterns

Extract Specific Fields

Extract only the fields you need from a large object:

{
  "name": "{{ trigger.user.name }}",
  "email": "{{ trigger.user.email }}",
  "created": "{{ new Date().toISOString() }}"
}

Merge Multiple Sources

Combine data from different steps:

{
  "userData": "{{ get_user.output }}",
  "orderData": "{{ get_orders.body }}",
  "timestamp": "{{ Date.now() }}"
}

Build Dynamic URLs

Construct URLs from variables:

{{ `https://api.example.com/users/${trigger.userId}/orders?limit=10` }}

Conditional Field Inclusion

Include fields only if they exist:

{
  "name": "{{ trigger.name }}",
  ...{{ trigger.email ? { email: trigger.email } : {} }}
}

Best Practices

Use Meaningful Step Names: Rename steps to reflect what they do (e.g., get_user instead of step_1)
Test Data Flow: Always test with real data to verify expressions work correctly
Handle Missing Data: Use null coalescing (??) or defaults for optional fields
Keep Expressions Simple: Complex logic should go in code actions
Document Complex Mappings: Add notes explaining non-obvious data transformations

Next Steps

Loops & Branches

Learn control flow and conditional logic

Code Actions

Write custom data transformations

Debugging

Debug data flow issues

Error Handling

Handle data errors gracefully

Building Workflows

Managing Workflows

Passing Data Between Steps

Understanding Step Outputs

Accessing Step Outputs

Variable Types

1. Step Outputs

2. Loop Variables

loop.item

loop.index

loop.iterations

3. Connections

4. Router/Branch Data

Using Expressions

String Operations

Number Operations

Array Operations

Object Operations

Data Mapping Examples

Example 1: Transform API Response

Example 2: Loop Over Items

Example 3: Conditional Data

Testing Data Flow

Sample Data

Advanced Data Techniques

Working with JSON

Date and Time

Error Handling in Expressions

Common Patterns

Best Practices

Next Steps

Loops & Branches

Code Actions

Debugging

Error Handling

Building Workflows

Managing Workflows

​Understanding Step Outputs

​Accessing Step Outputs

​Variable Types

​1. Step Outputs

​2. Loop Variables

loop.item

loop.index

loop.iterations

​3. Connections

​4. Router/Branch Data

​Using Expressions

​String Operations

​Number Operations

​Array Operations

​Object Operations

​Data Mapping Examples

​Example 1: Transform API Response

​Example 2: Loop Over Items

​Example 3: Conditional Data

​Testing Data Flow

​Sample Data

​Advanced Data Techniques

​Working with JSON

​Date and Time

​Error Handling in Expressions

​Common Patterns

​Best Practices

​Next Steps

Loops & Branches

Code Actions

Debugging

Error Handling

Understanding Step Outputs

Accessing Step Outputs

Variable Types

1. Step Outputs

2. Loop Variables

3. Connections

4. Router/Branch Data

Using Expressions

String Operations

Number Operations

Array Operations

Object Operations

Data Mapping Examples

Example 1: Transform API Response

Example 2: Loop Over Items

Example 3: Conditional Data

Testing Data Flow

Sample Data

Advanced Data Techniques

Working with JSON

Date and Time

Error Handling in Expressions

Common Patterns

Best Practices

Next Steps