Custom identifiers – Ometria Help Centre

Ometria identifies your customers using identifiers: pieces of information that point to a specific person. As standard, Ometria uses customer ID, email address, phone number, and the mobile app ID. Custom identifiers let you add your own, such as a loyalty ID or membership number, so Ometria can recognise and unify customers using the identifiers that matter to your business.

This article explains the options that control how an identifier behaves, and shows worked examples of how those options decide whether two contacts are kept separate or brought together.

💡 Availability: Custom identifiers are set up for each account individually, together with your Ometria team. Your existing identification is not affected. To discuss them for your account, speak to your Customer Success Representative.

Sending custom identifiers to Ometria

You send custom identifiers in the extra_identifiers field through the API, or as an extra_identifiers.<identifier> column in a CSV upload. For the exact format, see the API documentation and CSV Upload.

⚠️ Identifier values are case sensitive. LOYALTY#123 and loyalty#123 are treated as two different identifiers and will not match. Send each identifier consistently.

Identifier options

Each identifier is set up with options that control how Ometria uses it. Understanding what they mean helps you decide how your identifiers should behave.

Unique

Whether the identifier can only ever belong to one contact. A customer ID is usually unique, because it points to a single person. Something like an address would not be, because multipole people may live there.

Multiple values

Whether one contact can hold more than one value for the identifier. For example, a customer might collect several loyalty card numbers over time, and you want to keep all of them on their profile.

Priority

Which identifier Ometria trusts first when different identifiers point at different contacts. The identifier with the highest priority decides which profile is treated as the main one.

How identifiers decide what happens

When information reaches Ometria, it compares the identifiers on the incoming data with the identifiers on your existing contacts. One of three things happens:

A new contact is created when none of the identifiers match an existing contact.
The data is added to an existing contact when its identifiers match one contact.
Two contacts are merged when the incoming data links contacts that were previously separate, and their identifiers do not conflict. This happens only when automatic merging is enabled.

💡 Merging is optional, and separate from identification. As records arrive, Ometria always matches them to an existing profile where it can, and updates it. Merging is a further step that consolidates two profiles when they are found to be the same person, either as new data links them or as a later review of your existing profiles. You choose whether this happens automatically. With automatic merging switched off, Ometria still identifies and updates profiles as normal, but does not consolidate separate ones for you.

The examples below assume automatic merging is switched on and show how your identifier options change what happens.

Example 1: bringing a guest order and a sign-up together

A shopper places an order in store, identified only by a CRM ID (your own internal customer reference, for example from your CRM or order system). Separately, they sign up to your newsletter, identified only by their email. You now have two contacts:

Contact	CRM ID	Email
Contact A	CRM-500	(none)
Contact B	(none)	jane@example.com

Later, an online order arrives carrying both CRM ID CRM-500 and email jane@example.com. It matches Contact A on CRM ID and Contact B on email. Because neither contact holds a conflicting value, and automatic merging is enabled, Ometria merges them into one profile with both identifiers. The guest order and the sign-up are now the same person.

Example 2: priority decides the main profile

When incoming data matches more than one contact, the contact matched by the highest-priority identifier becomes the main profile that the others merge into. Suppose your priorities are:

Identifier	Priority
CRM ID	1 (highest)
Email	2
Loyalty ID	3

If an incoming record matches one contact by CRM ID and a different contact by loyalty ID, the contact matched by CRM ID is kept as the main profile, because CRM ID has the higher priority.

Example 3: a unique identifier prevents a merge

Identifiers marked unique protect against incorrect merges. If bringing two contacts together would place two different values on a unique identifier, Ometria treats this as a conflict and does not merge them.

Contact	CRM ID (unique)	Email
Contact A	CRM-100	jane@example.com
Contact B	CRM-200	jane@example.com

Both contacts share the same email, but they hold different CRM IDs, and CRM ID is unique. Merging them would put two CRM IDs on one profile, which is not allowed, so Ometria keeps them separate.

Example 4: a multi-valued identifier matches on any shared value

When an identifier allows multiple values, two contacts match if they share any value, and the differing values are not treated as a conflict. Suppose loyalty ID allows multiple values:

Contact	Loyalty IDs
Contact A	LOY-1, LOY-2
Incoming data	LOY-2, LOY-3

They share LOY-2, so the data is recognised as the same customer, and the profile ends up holding all three loyalty IDs. If loyalty ID were not multi-valued, LOY-1 and LOY-3 would conflict, and the merge would be blocked.

Identifier filters

Sometimes a value arrives that should never be treated as a real identifier, such as a placeholder email or a default ID used during testing. Left alone, values like these can wrongly link unrelated customers into one profile. Identifier filters tell Ometria to ignore specific values, so they are never used to identify or merge contacts.

Common values worth filtering:

Value	Why filter it
`noreply@example.com`	A placeholder email shared by many records.
`00000` or `-1`	Default or test customer IDs left over from development.
`guest` or `unknown`	Placeholder values used when a real identifier was missing.

Choosing your settings

When you plan a custom identifier with your Ometria team, these questions help decide its options:

Does this value belong to only one person? If yes, mark it unique.
Can one person have several of these over time? If yes, allow multiple values.
Which identifier should win when two disagree? Give your most trusted identifier the highest priority.
Are there placeholder or test values in your data? Add them as identifier filters so they never link customers.

Where custom identifiers appear

Once set up, custom identifiers appear alongside standard ones in the single customer view, and you can view them and export them within the segment explorer.

What this means for your account

Custom identifiers are additive. Your existing identification continues to work exactly as it does today. Custom identifiers and identifier filters are available to enable per account when you want them.

See also: