Full Answer

Open tracking and click tracking use fundamentally different mechanisms, which is why their accuracy differs significantly.

Open tracking depends entirely on image loading. Klaviyo inserts a clear (invisible) pixel image into the email body. When the recipient's email client renders the message and loads images, that pixel fires an HTTP request to Klaviyo's servers, which records the open event with a timestamp, device type, and approximate location derived from the IP address. If images are blocked — as they are by default in many corporate email clients — or if the email is read in plain text mode, the open never registers even though the recipient saw the content.

Apple Mail Privacy Protection adds another layer of unreliability. Since iOS 15, Apple pre-fetches email images through proxy servers regardless of whether the recipient actually opens the message, inflating open counts and masking real engagement data. This has made open rates increasingly unreliable as a standalone metric for any email platform, not just Klaviyo.

Click tracking is more accurate because it uses URL rewriting rather than image loading. Klaviyo replaces every link in the email with a redirect URL that routes through its tracking servers. When a recipient clicks, the redirect logs the event and then forwards them to the original destination. This mechanism works regardless of image-loading settings, which is why it is possible — and common — to see clicks recorded on emails that show zero opens.