Customer Counts: Ecommerce Customer ID vs Decile Unified ID

Counting Customers in Decile

Decile brings together customer data from your ecommerce platform and other sources, and along the way it works out which records actually belong to the same person. This article explains the difference between your ecommerce platform's customer ID and the Decile unified ID, why customer counts can differ depending on which one you use, and how the two are used in Decile's AI features.

What is an ecommerce platform customer ID?

Your ecommerce platform — Shopify, for example — gives every customer its own ID. It's the identifier that platform uses to track a shopper and their orders.

The catch is that one real person can end up with more than one customer record. Someone might check out as a guest once and create a profile later, use two different email addresses, or sign up again with a new phone number. Each of those creates a separate customer ID on your platform, even though it's the same human being.

Three "customers" each with a different email address.

What is the Decile unified ID?

The Decile unified ID identifies a person, rather than a single customer record. When Decile ingests your data, it looks for records that clearly belong to the same individual and links them together under a single unified ID.

So where your ecommerce platform might see three separate customer records, Decile may recognize them as one person and represent them with one unified ID. This gives you a truer picture of how many distinct customers you actually have, and lets Decile combine everything it knows about that person — across all their records — into one profile.

How identity resolution works

The process of linking records to the right person is called identity resolution. Decile primarily matches on two pieces of information:

• Email address

OR

• Phone number

When different customer records share the same email or phone number, Decile can confidently treat them as the same person and group them under one unified ID. This is what allows a shopper's full history to come together, even when it's spread across multiple logins or checkouts.

One "person" all sharing the same phone number.

Why counts can differ depending on the ID

Because one person can map to several customer records, counting by ecommerce customer ID and counting by Decile unified ID can produce different numbers — and both can be correct. They're simply answering different questions:

• Count by ecommerce customer ID answers "how many customer records are there?"
• Count by Decile unified ID answers "how many distinct people are there?"

The unified ID count will usually be lower than the raw customer-record count, since multiple records collapse into a single person. If you ever see two customer counts that don't match, this difference in what's being counted is almost always the reason.

Which ID the AI features use

In Decile's AI features — including Luma and the Decile MCP — the Decile unified ID is the primary identifier used for customer counts. By default, when you ask a question like "how many customers do I have?", you're getting a count of distinct people.

If you specifically want a count based on the source identifier from your ecommerce platform instead, you can say so in your request. Phrases like "by ecommerce customer id" or "count of Shopify ids" signal that you want the underlying platform ID used rather than the unified ID. For example:

• "How many customers bought in Q2?" → counted by Decile unified ID (distinct people)
• "How many customers bought in Q2 by ecommerce customer id?" → counted by the source platform ID (customer records)

This gives you the flexibility to look at your data either way, depending on the question you're trying to answer.

Frequently asked questions

Which count is the "right" one? Both are valid — they just measure different things. The Decile unified ID counts distinct people; your ecommerce customer ID counts customer records. Use whichever fits the question you're asking.

Why is my Decile customer count lower than the count in my ecommerce platform? Because Decile links multiple records that belong to the same person into a single unified ID. Several platform records can collapse into one person, which lowers the total.

What does Decile use to match records to a person? Primarily email address and phone number. When records share these details, Decile groups them under one unified ID.

Which ID do the AI features use by default? The Decile unified ID. Customer counts in Luma and the Decile MCP are based on distinct people unless you ask otherwise.

How do I get a count using my ecommerce platform's ID instead? Include a phrase like "by ecommerce customer id" or "count of Shopify ids" in your question, and the AI features will count by the source platform identifier rather than the unified ID.