HubSpot tracks visitors using browser cookies. Every time a visitor lands on your website, HubSpot will check for an existing tracking cookie. If one does not exist, a cookie will be associated with that visitor and will log every page that person visits moving forward.
There are a few things to be aware of in regards to how HubSpot handles tracking cookies:
Visitors will be tracked anonymously even before they become contacts. If and when a visitor fills out a form, HubSpot will associate their previous page views based on the tracking cookie. If the email address filled in the form is associated with an existing contact, this visitor will be identified as the contact. This includes contacts that were imported.
If a visitor deletes their cookies, they will be considered a new visitor and will be assigned a new cookie. However, HubSpot will automatically deduplicate form submissions coming from the same email address, even if different browser cookies were associated with the submissions.
Since cookies are unique to a browser, if two people share a single computer, their submissions will be associated with the same contact record. This deduplication by cookie ensures that if a contact submits forms on your website using different email addresses, all submissions are associated with a single contact record in HubSpot.
HubSpot does not trackunique visitors. This metric is based on user behavior and is not always reliable. A user may clear their cookies, use a different browser, or block cookies. All of these actions will count multiple unique visitors for the same actual visitor.
HubSpot will attribute page views to a contact if the contact clicks a link in a tracked marketing email which directs to a page with the HubSpot tracking code installed.
The HubSpot tracking code will make asynchronous requests to several HubSpot domains, such as track.hubspot.com and forms.hubspot.com. HubSpot serves these scripts on multiple domains to decrease the chance of any single script failing to load, which can occur if a visitor is using a browser extension that blocks some HubSpot domains.