Unique identifier (UID)
Also known as: UID, unique ID
In short
A unique identifier (UID) is a value assigned to a single record, such as a contact, account, or company, that distinguishes it from every other record in a dataset. No two records share the same value.
UIDs let systems tell records apart even when names change or look alike. They are the backbone of deduplication, enrichment, and syncing data between a CRM, a marketing tool, and a data warehouse.
Common unique identifiers in GTM data
- Record ID: The internal ID your CRM assigns to each contact, account, or deal.
- Email address: Often used as the key for contacts, though people change jobs and addresses.
- Domain: A frequent key for companies, since a website domain is usually stable and distinct.
- External ID: An ID from another system, stored so records can be matched across tools.
- Vendor ID: An identifier from a data provider that points to a specific company or person record.
What makes a good identifier
Emails and names fail some of these tests. A person changes email when they change jobs, and two people can share a name. That is why many teams use a system ID as the primary key and treat email or domain as a matching field.
- Unique: One value points to one record.
- Stable: It does not change when a name, title, or address changes.
- Always present: Every record has one, with no blanks.
- Meaningless: A system-generated ID is safer than one built from data that can change.
Why UIDs matter for revenue teams
Deduplication
Matching on a unique key stops the same company appearing twice and splitting activity between records.
Enrichment and sync
When you enrich or sync records, the UID tells the system which record to update instead of creating a new one.
Reporting
Clean keys make joins between CRM, billing, and product data reliable, so pipeline and revenue numbers agree.
Example
Say a company imports a list where one account appears as "Acme Inc" and another as "Acme, Incorporated". Without a shared key they become two accounts. If both carry the same domain or external ID, the system can match them and merge the duplicates.
Common mistakes
- Using email as the only key for contacts who change jobs.
- Matching accounts on company name instead of domain or ID.
- Not storing external IDs, which makes later syncs guesswork.
- Reusing or editing IDs after records are created.
Unique identifier FAQs
What is a unique identifier (UID)?
A unique identifier is a value assigned to one record, such as a contact or company, that sets it apart from all others. Systems use it to match, update, and merge records reliably, even when names or other fields change.
What are examples of unique identifiers in a CRM?
Common examples include the CRM record ID, email address for contacts, website domain for companies, and external IDs from other tools or data providers. System-generated record IDs are the most stable because they never depend on changing data.
Is email address a good unique identifier?
It works as a matching key for contacts but is not ideal as a primary ID. People change jobs and email addresses, and shared inboxes can map to many people. A system-generated ID is safer, with email as a matching field.
Why do unique identifiers matter for data enrichment?
They tell the system which existing record to update with new data. Without a reliable key, enrichment can create duplicates or overwrite the wrong record, which hurts data quality and reporting.
