HubSpot tracks every visitor that comes to your site using browser cookies. Every time a visitor lands on your website, HubSpot will check for the presence of an existing tracking cookie. If a tracking cookie doesn't exist, HubSpot spins up a unique browser cookie for that visitor and will log every page that person visits moving forward.
HubSpot will track the page view activity of each visitor anonymously even before he or she becomes a contact. For example, if a person visits your website three separate times before filling out a form, HubSpot will still include the previous visits in the contact timeline, provided all these visits occurred on the same browser.
The cookies are set to never expire. Since HubSpot uses a cookie to track visitors, if a visitor deletes her cookies, he or she will be considered a new visitor and will be assigned a new cookie. HubSpot will, however, automatically merge multiple browser cookies together if the submissions come from the same email address. The same is true for multiple submissions on a single browser. Since cookies are unique to a browser, if two people share a single computer, their submissions will be merged into a single contact record. Contact merging by cookie exists to ensure that if a contact submits multiple forms on your website using different email addresses, they are merged into a single record in HubSpot since they are both the same contact.
When testing submissions on your forms, it is important to be aware of this. If you submit multiple tests from one single browser with different email addresses, these submissions will be merged into a single contact record in HubSpot due to the presence of a common tracking cookie. The best way to test submissions, if you don't want them to be merged together is to test in the private browsing mode of your web browser. This ensures that you are given a new tracking cookie for each private browsing session.