How do “read,” “skim,” and “glanced” categories get defined?

You send a campaign, check your analytics, and see three tidy little buckets: Read, Skimmed, Glanced. But where do those labels actually come from? Not from some universal standard. They come from a simple clock.

Most ESPs that offer this kind of engagement breakdown are measuring one thing: how long your email stayed open after the tracking pixel fired. That's it. The clock starts when the open is registered, and it stops when the email is closed. Then the platform slots that duration into one of three buckets based on a time threshold it set internally.

The rough industry convention looks like this:

• Glanced means the email was open for roughly 2 seconds or less. The reader opened it, maybe saw the subject line preview, and moved on.
• Skimmed sits in the middle, typically 2 to 8 seconds. Long enough to scan headlines or spot a key visual, but probably not to read body copy.
• Read means the email was open for 8 seconds or more. Some platforms set this threshold at 10 or even 15 seconds depending on their internal definitions.

Here's the part that matters: these thresholds aren't standardized across the industry. Mailchimp doesn't define "Read" the same way Klaviyo does, and neither of them publishes their exact numbers publicly. So when you're comparing engagement data between two platforms, the categories might look the same but measure differently underneath.

There's another wrinkle worth knowing. Apple Mail's Mail Privacy Protection (MPP) pre-fetches tracking pixels the moment an email arrives, regardless of whether anyone actually opened the message. That fires the clock before a human ever looks at your email, which means a chunk of your "Read" data could actually be machine-triggered opens clocking in at zero real seconds. The categories still get assigned, but they don't reflect genuine reading behavior for that portion of your list.

So what should you actually do with these categories? They're most useful as a relative signal, not an absolute one. If your "Glanced" rate is climbing over time for the same audience, something about your content or timing is probably off. If a specific segment consistently lands in "Read," that's your engaged core and worth treating differently in segmentation. Just don't treat the numbers as precise science.

Want to understand how the underlying dwell time measurement actually works before interpreting these buckets? That's a good place to start. And if you're trying to build smarter segments from engagement data and aren't sure which ESP gives you the most useful signals, feel free to ask us directly. No pitch, just a straight answer.