How HubSpot UTK Works with Vector

Last updated: December 5, 2025

Overview

HubSpot assigns a unique visitor ID (called a UTK) to website visitors to help track their behavior. Vector can read this UTK and use it to identify who a visitor is and match them to their contact record in HubSpot.

By doing this, Vector can link anonymous traffic to known contacts and ensure accurate syncing back into HubSpot.

How the Flow Works

1. HubSpot Creates a Visitor ID (UTK)

When someone visits a page that has HubSpot tracking installed:

  • HubSpot automatically assigns a unique ID (UTK) to the visitor

  • That UTK is stored in the visitor’s browser

  • The UTK acts like a digital “name tag” for tracking web activity

2. Vector Reads the UTK

When the Vector pixel is active on the same website:

  • Vector loads alongside the HubSpot script

  • Vector looks for the UTK stored in the visitor’s browser

  • If found, Vector includes this UTK when sending visitor data to Vector’s servers

3. Vector Identifies the User

Once the UTK is received:

  • Vector sends the UTK to its servers

  • Vector then asks HubSpot if the UTK is linked to an existing HubSpot contact

  • If HubSpot has a matching contact, HubSpot returns key contact details such as:

    • Email address

    • Name

    • Company

    • Contact metadata the customer allows

Vector then associates this contact information with the visitor.

4. Vector Stores and Uses the UTK

After matching is complete:

  • Vector stores the UTK and related contact data in its database

  • When syncing records back into HubSpot, Vector uses the stored UTK to match visitors to the correct HubSpot contact record

  • This ensures Vector updates the correct person without creating duplicates

Visual Flow

Visitor visits your website
        ↓
HubSpot creates a UTK and stores it in the browser
        ↓
Vector pixel reads the UTK
        ↓
Vector sends UTK to Vector servers
        ↓
Vector asks HubSpot: "Who is this UTK?"
        ↓
HubSpot responds with contact info (if matched)
        ↓
Vector stores UTK and contact metadata
        ↓
Vector uses the UTK later to sync back to HubSpot

What Vector CAN Do with UTK

  • Identify existing HubSpot contacts using UTKs

  • Match anonymous visitors to known contacts when HubSpot has a record

  • Store UTKs for future syncing and deduplication

What Vector CANNOT Do with UTK

  • Vector cannot assign UTKs to new contacts created in HubSpot

HubSpot controls UTK creation and assignment, and it only happens automatically when website tracking is enabled.

Why?

To protect accuracy and avoid:

  • Duplicate UTKs

  • Incorrect mapping of web activity to the wrong contacts

  • Inaccurate attribution or visitor tracking

Because of this, UTKs must always come from HubSpot—not from external systems.