To track opens, we place a small image at the bottom of each campaign, known as a pixel. When the pixel loads, we assume the email has been opened, and this is reflected in your GiantCampaign reports. 

This can happen before you open it. A small number of email clients, firewalls, and anti-virus products automatically load images within an email as soon as it is received, a practice known as image pre-fetching. Because the pixel loads in both cases, it's impossible to tell the difference between a genuine open and an image pre-fetch performed by the email client - so, while opens are a great indicator of who is engaging with your emails, they're not always 100% accurate.

Following the release of iOS15 by Apple, you should see an increase in open rates, especially among contacts who use Apple devices and have updated to the new iOS version. To protect their users' privacy, iOS15 has made changes to how they handle emails, and emails delivered to a mailbox connected to the Apple Mail app (on iPhone, iPad, and Mac) will have images pre-fetched while the device is using WiFI. As a result, emails may be marked as "opened" before you or your readers open them.