Why did my Klaviyo open rate drop?

Open rate is downstream of whether the email arrived in the inbox at all. If placement slipped — more mail routing to spam or promotions — opens fall even if everything else is fine. Look for a step-change that lines up with a spike in send volume, a new sending domain, or a content change. Deliverability is the first thing to rule out because it invalidates every other reading.

Apple Mail Privacy Protection pre-fetches images, which can inflate or distort open rates. A reported change in opens can be an artifact of MPP proxy-opens rather than real human behaviour — especially if your Apple-heavy segments moved and your click rate didn't. If clicks held steady while opens dropped, be suspicious that the drop is measurement, not engagement.

Sending to a stale or over-broad list drags engagement down and, over time, your sender reputation with it — which then feeds back into placement. Check whether you recently widened a segment, imported a list, or stopped suppressing unengaged profiles. A reputation dip is slower-moving than a single-send blip and usually shows as a downward trend across several sends, not one.

Only after placement, MPP, and list health should you look at the creative variables. A subject-line pattern that resembles a low-engagement family, a send time outside your audience's window, or a from-name change can all move opens. These are the easiest to A/B test — but they're last on the list because they're the smallest effect if the earlier causes are in play.

This checklist is exactly the reasoning Campaign Copilot automates. It watches your open rate against a 14-day rolling baseline, flags a deviation before it costs you a send cycle, names the likely root cause in plain English with a confidence score, and recommends a fix. It's read-only — it diagnoses and recommends, and you decide whether to apply the fix. It doesn't run your campaigns for you.