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Metrics type: Supporting Metrics • Category: Email Marketing
Open rate plotted over time. Apple Mail Privacy Protection auto-opens make the absolute level meaningless, so read the shape of the line, not the number on it.

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At a glance

The time-series of email open rate across the selected period, one point per period bucket. Each point is opens_unique ÷ delivered for sends in that bucket. Since Apple’s Mail Privacy Protection (MPP) pre-fetches images and registers an open whether or not a human looked, a large and unknowable share of these opens are machine opens. Treat the absolute level as inflated and the trend line as directional. A sudden step-change down in this line is far more diagnostic than the headline percentage, it usually flags a deliverability or inbox-placement problem rather than a sudden loss of human interest.

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Calculation

Calculated automatically from your Klaviyo data. See the At a glance summary above for what the metric tracks and the worked example below for a typical reading.

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Worked example

An illustrative homeware brand sending two to three Klaviyo campaigns a week. Reading the dashboard on 14 Apr 26 for the trailing 30 days (14 Mar 26 to 12 Apr 26), the open-rate line by week looks like this (figures are illustrative, not a real merchant’s data):
Five observations:
  1. The 46% headline is inflated by MPP and should not be read as “46% of humans opened”. For an iOS-skewed homeware audience, a large slice of those opens are Apple Mail pre-fetches. The useful information here is that the line normally sits around 45%, not that the level is high.
  2. Week 3’s drop to 36% is the real signal. A nine-point step down in a single week, against an otherwise flat line, is the kind of move worth investigating. Because MPP opens are roughly constant, a drop this size usually means fewer messages actually reached the inbox (more landed in spam or Promotions, or a deliverability dip), not that humans suddenly lost interest.
  3. Always pair the step-down with delivery-rate and bounce data. If Delivery Rate also dipped in week 3, that confirms an inbox-placement story. If delivery held steady, the cause may instead be a weak send (a poorly targeted segment or a dull subject line) rather than a systemic problem.
  4. Week 4 recovering to 44% suggests the week 3 dip was transient. A one-week dip that self-corrects is common after a single underperforming campaign. A two- or three-week sustained decline is the pattern that warrants escalation to a deliverability review.
  5. For a cleaner human-interest read, cross-check the click line. Clicks are not MPP-affected, so if Click Rate Trend is flat while this open line wobbles, the wobble is almost certainly MPP noise or inbox placement, not a change in real engagement.

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Sibling cards merchants should reference together

Open Rate Trend is a directional engagement signal. Pair it with these to separate MPP noise from real movement:

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Reconciling against Klaviyo

Where to look in Klaviyo:
  • Klaviyo → Analytics → Performance, then the open-rate metric over time, for the account-level trend.
  • Klaviyo → Campaigns, then open a campaign to see its individual open rate, useful for attributing a trend dip to a specific send.
  • Klaviyo → Analytics, then the Opened Email metric in Metric reporting, which underlies the rate.
Why our number may legitimately differ:

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Known limitations / merchant FAQs

Why is my open rate so high, like 50%+? Apple Mail Privacy Protection. When an Apple Mail user has MPP on (it is on by default and the majority do), Apple pre-fetches your email images from its own servers, which registers an open whether or not a human ever looked. For iOS-heavy lists this can add 20-40 points of phantom opens. The high number is real machine activity, not real human interest. Read the trend, not the level. So is the open rate useless? Not useless, just directional. The MPP share is roughly stable week to week, so the shape of the line still tells you something: a sudden sustained drop almost always means an inbox-placement or deliverability problem, because that is one of the few things that moves opens independently of MPP. For a clean human-interest read, use click rate and click-to-open rate, which MPP does not touch. The line dropped and stayed down. What do I check first? Deliverability. Check Delivery Rate, Bounce Rate, and Sender Reputation Risk. A sustained open-rate decline with rising bounces or spam complaints points to a reputation issue. If delivery held steady, look instead at whether you changed segments, subject-line style, or send time. Does this include flows or just campaigns? The trend blends both campaign and flow sends by default so it reflects total program engagement. If you want campaign-only or flow-only, filter accordingly in Klaviyo, where campaign-values and flow-values reports are separated. Why does my number differ from Klaviyo’s dashboard? Usually period boundaries (our 30-day rolling vs Klaviyo’s calendar months), time-zone bucketing (UTC vs account zone), or an MPP filter being on in one view and off in the other. Match those settings before treating it as a real divergence. Can I set an alert on a fixed open-rate threshold? You can, but a fixed threshold is weak for opens because of MPP inflation. A step-change alert (a sustained drop relative to the recent baseline) is far more meaningful here than a hard floor. Alert thresholds are configurable per profile in the Alert Rules tab.

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Tracked live in Vortex IQ Nerve Centre

Open Rate Trend is one of hundreds of KPI pulses Vortex IQ tracks across Klaviyo and 70+ other ecommerce connectors. Nerve Centre runs the detection layer; Vortex Mind investigates the cause when something moves; Ask Viq lets you interrogate any number in plain English. Start for free or book a demo to see this metric running on your own data.