Customer Metafield Update

We will assume the following scenario to understand how we can use the Customer Metafield Update trigger from the Flow Trigger Extensions app to tag products based on a customer's clothing size preference.

Scenario: Customer updates their size → All matching products are automatically tagged

A fashion retailer lets customers save their preferred clothing size in their profile. Every time a customer updates their size, Flow automatically finds all products available in that size and tags them, making it easy to build size-based collections, filters, and personalized recommendations.

How to build this flow

You can build this flow by following these 2 steps:

1. Add the Customer Metafield Trigger in the app

2. Create the Shopify Flow

You can also see these steps in the demo video below (video has no voice):

1) Add trigger to Customer Metafield

First you need to register the trigger on the customer metafield you want to monitor.

• First make sure you have the Customer Access from the Flow Trigger Extension → Dashboard → Setup Guide you will see the Grant Customer access, you can also see the permissions from the Flow Trigger Extension → Permissions

• Then you have to create the Customer metafield trigger. If you do not see the Setup Guide, navigate directly to the app's metafield triggers page.

• Press the Add Trigger button to create a new trigger.

• Select the resource type Customer and search for the metafield custom.clothing_size. Select it and press the Add Trigger button to confirm.

2) Create the Shopify Flow

Now create the Flow that finds matching products and tags them whenever the customer's size is updated.

• Open Shopify Flow and create a blank workflow. Select the Metafield Update trigger from the Flow Trigger Extensions app.

• Click Record Event, then in a new tab update a customer's custom.clothing_size metafield to "XL" to capture a sample payload. Click Select Test Event to load the recorded payload into the workflow builder.

• You will see the payload containing the customer data and the new metafield value. This holds the new size value the customer just set (e.g. "XL").

• Add a Condition to check that the metafield value is not blank AND metafield.key = "clothing_size" AND resourceType = "CUSTOMER"

• Add an Action: Get product variant data and filter by variant option1 matching the metafield value: Variant option1 == {{ metafield.value }} This retrieves all products that have a variant in the customer's size.

• Add an Action: Add tag to product for each product returned: available-in-{{ metafield.value }} For a customer who set size "XL", this adds the tag available-in-XL to every matching product.

• Optionally, add an Action: Add tag to customer to keep the customer record in sync: size-{{ metafield.value }}