How to Use Custom Code in Zapier

Custom code in Zapier lets you handle complex logic inside your Zaps without leaving the platform. This guide walks you through enabling, creating, editing, and testing custom code steps so you can build more powerful automations.

The custom code feature is currently in beta and is gradually rolling out to users. Interface details and availability may change as Zapier updates this experience.

What the Zapier Custom Code Feature Does

The custom code step gives you a flexible way to transform data and add logic where standard Zap steps are not enough.

With a custom code step, you can:

• Write JavaScript or Python to transform or validate data.
• Branch logic based on conditions (for example, if/else checks).
• Reformat text, numbers, or dates before sending them to another step.
• Combine multiple input fields into a single output object.

This step runs inside your Zap, between triggers and other actions, so you can chain the output of your code to any following steps.

Access Requirements for Zapier Custom Code

Custom code in Zapier is available in beta and may not yet appear for all users.

• You may see a banner or notification in your Zap editor when the feature is enabled for your account.
• If you do not see the custom code option as a step type, it is likely not yet enabled on your workspace.
• Zapier may adjust the layout, labels, or available options as the beta progresses.

Once enabled, you can add a custom code step to any new or existing Zap.

How to Add a Custom Code Step in Zapier

Follow these steps to insert a custom code step into your Zap:

1. Open your Zap in the editor.

2. Hover between two steps or click the + button where you want to add code.

3. In the action picker, search for the custom code option.

4. Select the custom code step and click to add it to your Zap.

5. Choose your programming language if prompted (for example, JavaScript or Python).

After you add the step, the editor displays panels for writing code and configuring inputs and outputs.

Configure Zapier Custom Code Inputs and Outputs

The custom code step processes data from earlier steps and returns structured outputs for later steps.

Set Inputs for Your Zapier Code Step

Inputs let you pass fields from previous steps into your code.

1. In the custom code step, locate the Inputs section.

2. Add each input you need by giving it a clear name.

3. Use the field selector to map values from earlier Zap triggers or actions.

4. Repeat for all data points your code should receive.

These inputs become variables you can reference in your script, typically through a dictionary or object structure provided by the Zap editor.

Define Outputs from Zapier Custom Code

Outputs are the data your code sends to later steps.

1. In the Outputs or Return values area, identify the variables or object keys your code will return.

2. Ensure each output has a descriptive name so you can recognize it in downstream steps.

3. In your script, return an object or dictionary that matches the structure defined here.

After testing the code step, Zapier displays sample output values you can map into later actions.

Write and Edit Code in Zapier

The custom code editor in Zapier is designed for small, focused transformations and logic.

Write Your Script

Inside the code panel you can:

• Reference input variables provided by the step.
• Apply any supported language features within the execution limits.
• Return a final object containing all data you want to pass forward.

Keep code concise and focused on a single responsibility, such as formatting, filtering, or conditional routing.

Edit and Update Existing Zapier Code

To modify a custom code step in an existing Zap:

1. Open the Zap in the editor.

2. Click the custom code step you want to update.

3. Adjust the script, inputs, or outputs as needed.

4. Click to save any changes and re-test the step.

Each time you edit, run a test so you can confirm the behavior before turning your Zap back on.

Test and Troubleshoot Custom Code in Zapier

Testing ensures your Zapier custom code works correctly with real sample data.

Run a Test of the Code Step

1. Make sure earlier steps in your Zap have test data available.

2. Open the custom code step and confirm your inputs are mapped correctly.

3. Click the Test button for the code step.

4. Wait for the execution results to appear in the output panel.

The test run shows the returned outputs so you can verify field names and values.

Fix Common Errors in Zapier Custom Code

If the code step fails, you may see error messages related to syntax, missing inputs, or unexpected data types.

• Review the error details shown in the step.
• Confirm that all required inputs contain test data.
• Check that you are returning a valid object with the expected keys.
• Update your code and re-test until the step runs successfully.

Once the test passes, continue testing the remaining steps in your Zap.

Best Practices for Using Zapier Custom Code

To keep your automations maintainable and reliable, follow these guidelines when working with custom code in Zapier.

• Keep code small and focused: Use separate code steps for clearly different tasks instead of one very large script.
• Use descriptive names: Name inputs and outputs clearly so anyone reviewing the Zap can understand what they represent.
• Handle unexpected data: Add checks for empty or invalid inputs to reduce runtime errors.
• Document complex logic: Add comments in your script when behavior is not obvious.

Remember that this feature is in beta, and some behaviors may change as Zapier continues development.

Where to Learn More About Zapier Custom Code

For full reference details and the latest interface updates, see the official Zapier help article on custom code: Effortlessly write custom code in your Zaps (Beta).

If you need professional help planning or optimizing complex workflows that rely on code and AI, you can also explore automation and AI consulting services at Consultevo.

By carefully configuring your inputs, outputs, and test strategy, you can use the custom code step in Zapier to cover advanced use cases that standard actions cannot handle on their own.