[GTM glossary](/glossary.md) Unique identifier Data & Enrichment # 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. Share term --- ## More related phrases * [Single source of truth](/glossary/single-source-of-truth.md) * [Entity resolution](/glossary/entity-resolution.md) * [Account enrichment](/glossary/account-enrichment.md) ## Similar phrases * [Data deduplication](/glossary/data-deduplication.md) Data deduplication is the process of finding and merging duplicate records, such as the same company or contact entered twice, so each real entity has one clean record. * [Golden record](/glossary/golden-record.md) A golden record is the single, most accurate and complete version of a customer, contact, or account, built by merging duplicate and conflicting records from many systems. * [System of record (SoR)](/glossary/system-of-record.md) A system of record is the application designated as the authoritative source for a specific type of data, such as accounts and opportunities in a CRM. * [Data hygiene](/glossary/data-hygiene.md) Data hygiene is the ongoing practice of keeping CRM and marketing data clean, accurate, consistent, and usable through regular checks, standards, and ownership. * [Match rate](/glossary/match-rate.md) Match rate is the percentage of records you submit to a data tool that it successfully identifies and returns data for, and it is the first number to check when comparing enrichment sources.