Tend has two ways to identify people even if they don’t fill out a form.
AutoID allows you to automatically identify the visitor based on a unique URL. You create a URL with an email address as a parameter in the URL.
When someone clicks on that parameter Tend associates the visit with that email address, without requiring them to enter their email address into a form. Note that you must know their email ahead of time and they need to click on a unique tracking link.
Here’s an example of how you could to that with your Mailchimp email list:
You can learn more about how AutoID works here: https://tend.io/blog/auto-id-website-visitors
TendID lets you to associate email addresses to visitors using code. This is useful when you already know who the user is visiting your site, usually because you are storing their information in a cookie.
See code examples and more details on TendID here: https://tend.io/docs/Setting-up-Tend/TendID